ref: 390e726c64ee2aca967617ac7f7fd2a44f27646b
dir: /sub.c/
#include "all.h"
extern Srv mysrv;
u64
newqpaths(u8 n)
{
u64 qpath;
Iobuf *sb;
Dentry *s;
sb = egetmetachk(Bdsuper, Bwritable, Tdentry, Qpsuper);
s = sb->d;
qpath = s->qidgen;
s->qidgen += n;
putbuf(sb, 1);
return qpath;
}
u64
newqpath()
{
return newqpaths(1);
}
/*
* what are legal characters in a name?
* only disallow control characters.
* a) utf avoids control characters.
* b) '/' may not be the separator
*/
int
checkname(char *n)
{
int i, c;
for(i=0; i<strlen(n); i++) {
c = *n & 0xff;
if(c == 0) {
if(i == 0)
return 1;
return 0;
}
if(c <= 040)
return 1;
n++;
}
return 1; /* too long */
}
u64
min(u64 a, u64 b)
{
if(a<b)
return a;
else
return b;
}
/* identify if the block is being used as a backup block */
int
isbkp(u64 bno)
{
if(bno == config.config.dest[0] ||
bno == config.super.dest[0] ||
bno == config.root.dest[0])
return 1;
else
return 0;
}
/* making the assumption that all allocations are not readonly */
Iobuf *
allocblocks(u64 len, int tag, u64 qpath)
{
u64 blkno;
Iobuf *buf;
if(len > Maxdatablockunits)
panic("allocblocks(): invalid len %llud tag %s qpath %llud\n",
len, tagnames[tag], qpath);
ualloc(&frees, len, &blkno);
if(chatty9p > 1)
dprint("alloc %llud\n", blkno);
/* cannot do getbufchk() unless we ream the whole disk at start */
buf = getbuf(blkno, len, Bwritable, Bfreshalloc, getcallerpc(&len));
/* clear the buf to avoid leaks on reuse */
memset(buf->xiobuf, 0, len*Blocksize);
if(tag == Tdata){
buf->io->len = len;
buf->xiobuf64[len*Nu64perblock -1] = qpath;
}
settag(buf, tag, qpath);
return buf;
}
Iobuf *
allocmeta(int tag, u64 qpath)
{
return allocblocks(1, tag, qpath);
}
u8
allocdentries(u16 n, Iobuf **iobufs, u64 qpath)
{
u8 i, j;
for(i = 0; i < n; i++){
iobufs[i] = allocblocks(1, Tdentry, qpath+i);
if(iobufs[i] == nil){
for(j = 0; j < i; j++)
freeblockbuf(iobufs[j]);
return i;
}
iobufs[i]->d->qpath = qpath+i;
}
return i;
}
/* the buf should have been wlock()'ed */
void
freeblockbuf(Iobuf *buf)
{
if(buf->readers)
panic("freeblockbuf without Bwritable");
buf->tag = Tblank;
/* clear the buf to avoid leaks on reuse */
memset(buf->xiobuf, 0, buf->len*Blocksize);
ufree(&frees, buf->blkno, buf->len);
putbuf(buf, 0);
}
/* add the block to the extents used to manage free blocks */
void
freeblocks(u64 blkno, u64 len, u16 tag, u64 qpath)
{
Iobuf *buf;
if(blkno == 0 || blkno > config.nblocks){
panic("freeblock: bad addr %llud, nblocks %llud\n",
blkno, config.nblocks);
return;
}
buf = egetbufchk(blkno, len, Bwritable, tag, qpath, getcallerpc(&blkno));
freeblockbuf(buf);
}
int
Gfmt(Fmt *f1)
{
u16 t;
t = va_arg(f1->args, u16);
if(t < MAXTAG)
return fmtstrcpy(f1, tagnames[t]);
else
return fmtprint(f1, "<badtag %d>", t);
}
void
formatinit(void)
{
fmtinstall('G', Gfmt); /* print tags */
}
/* should be called with wlock(t)? */
void
fsok(int ok)
{
Iobuf *sb;
Dentry *s;
sb = egetmetachk(Bdsuper, Bwritable, Tdentry, Qpsuper);
s = sb->d;
s->fsok = ok;
if(chatty9p > 1){
dprint("fsok ok %d\n", ok);
showsuper(2, (u8*)s);
}
putbuf(sb, 1);
}
void
closefd(int fd)
{
if(fd != -1)
close(fd);
}
void
reamfile(u64 dblkno, u64 qpath, char *name, u64 size, u64 pdblkno, u64 pqpath, u64 preli, u8 flags)
{
Iobuf *b;
Dentry *d;
b = egetmeta(dblkno, Bwritable, Bfreshalloc);
settag(b, Tdentry, qpath);
d = b->d;
USED(name);
/* d->namelen = strlen(name);
strcpy(d->name, name);*/
d->flags = flags;
d->uid = d->muid = d->gid = -1;
d->mode =
((DMREAD) << 6) |
((DMREAD) << 3) |
((DMREAD) << 0);
d->qpath = qpath;
d->version = 1;
d->mtime = nsec();
d->size = size;
d->pdblkno = pdblkno;
d->pqpath = pqpath;
d->preli = preli;
putbuf(b, 1);
}
/*
The reamer is added to the adm group.
The ctl file is owned by the ream'er and the adm group.
*/
char magic[] = "mafs device\n";
void
reamdefaults(u64 bdconfig0, u64 bdsuper0, u64 bdroot0)
{
Iobuf *b;
Dentry *d;
char users[128+Userlen*3], cbuf[Ddatasize];
char inle[] = "0 439 440\n\0";
char *user;
int userslen, n;
user = getuser();
userslen = snprint(users, 128+Userlen*3, "-1:adm:adm:%s\n"
"0:none:adm:\n" /* user ID for "none" */
"9999:noworld::\n" /* conventional id for "noworld" group */
"10000:sys::\n"
"10001:upas:upas:\n" /* what is this for? */
"10006:%s:%s:\n", user, user, user);
/* cannot show this in /a though as the block number is 0 */
b = egetmeta(Bdmagic, Bwritable, Bfreshalloc);
settag(b, Tdentry, Qpmagic);
d = b->d;
// d->namelen = 5;
// strncpy(d->name, "magic", 6);
d->uid = d->muid = d->gid = -1;
d->mode =
((DMREAD) << 6) |
((DMREAD) << 3) |
((DMREAD) << 0);
d->qpath = Qpmagic;
d->version = 1;
d->mtime = nsec();
d->pdblkno = Bda;
d->pqpath = Qpa;
d->preli = 0;
n = snprint((s8*)d->buf, Ddatasize, "%s%llud\n",
magic, Blocksize);
d->size = n;
putbuf(b, 1);
b = egetmeta(Bdrootnames, Bwritable, Bfreshalloc);
settag(b, Tdentry, Qprootnames);
d = b->d;
d->flags = Fsys|Fn;
d->uid = d->muid = d->gid = -1;
d->mode =
((DMREAD) << 6) |
((DMREAD) << 3) |
((DMREAD) << 0);
d->qpath = Qprootnames;
d->version = 1;
d->mtime = nsec();
d->pdblkno = Bdroot;
d->pqpath = Qproot;
d->preli = In;
putbuf(b, 1);
b = egetmeta(Bdrootlnames, Bwritable, Bfreshalloc);
settag(b, Tdentry, Qprootlnames);
d = b->d;
d->flags = Fsys;
d->uid = d->muid = d->gid = -1;
d->mode =
((DMREAD) << 6) |
((DMREAD) << 3) |
((DMREAD) << 0);
d->qpath = Qprootlnames;
d->version = 1;
d->mtime = nsec();
d->pdblkno = Bdroot;
d->pqpath = Qproot;
d->preli = Inl;
putbuf(b, 1);
b = egetmeta(Bdrootlnamesextents, Bwritable, Bfreshalloc);
settag(b, Tdentry, Qprootlnamesextents);
d = b->d;
d->flags = Fsys|Fe;
d->uid = d->muid = d->gid = -1;
d->mode =
((DMREAD) << 6) |
((DMREAD) << 3) |
((DMREAD) << 0);
d->qpath = Qprootlnamesextents;
d->version = 1;
d->mtime = nsec();
d->pdblkno = Bdroot;
d->pqpath = Qproot;
d->preli = Inle;
d->size = sizeof inle;
strcpy((s8*)d->buf, inle);
putbuf(b, 1);
b = egetmeta(Bdroot, Bwritable, Bfreshalloc);
settag(b, Tdentry, Qproot);
d = b->d;
d->uid = d->muid = -1;
d->gid = -1;
d->mode = DMDIR |
((DMREAD|DMWRITE|DMEXEC) << 6) |
((DMREAD|DMWRITE|DMEXEC) << 3) |
((DMREAD|DMWRITE|DMEXEC) << 0);
d->qpath = Qproot;
d->version = 1;
d->mtime = nsec();
d->dblocks[0] = Bdrootnames;
d->dblocks[1] = Bdrootlnames;
d->dblocks[2] = Bdrootlnamesextents;
d->dblocks[3] = Bda;
addname(d, -1, 0, ".n");
addname(d, -1, 1, ".nl");
addname(d, -1, 2, ".nle");
addname(d, -1, 3, "a");
putbuf(b, 1);
b = egetmeta(Bdanames, Bwritable, Bfreshalloc);
settag(b, Tdentry, Qpanames);
d = b->d;
d->flags = Fsys|Fn;
d->uid = d->muid = d->gid = -1;
d->mode =
((DMREAD) << 6) |
((DMREAD) << 3) |
((DMREAD) << 0);
d->qpath = Qpanames;
d->version = 1;
d->mtime = nsec();
d->pdblkno = Bda;
d->pqpath = Qpa;
d->preli = In;
putbuf(b, 1);
b = egetmeta(Bdalnames, Bwritable, Bfreshalloc);
settag(b, Tdentry, Qpalnames);
d = b->d;
d->flags = Fsys;
d->uid = d->muid = d->gid = -1;
d->mode =
((DMREAD) << 6) |
((DMREAD) << 3) |
((DMREAD) << 0);
d->qpath = Qpalnames;
d->version = 1;
d->mtime = nsec();
d->pdblkno = Bda;
d->pqpath = Qpa;
d->preli = Inl;
putbuf(b, 1);
b = egetmeta(Bdalnamesextents, Bwritable, Bfreshalloc);
settag(b, Tdentry, Qpalnamesextents);
d = b->d;
d->flags = Fsys|Fe;
d->uid = d->muid = d->gid = -1;
d->mode =
((DMREAD) << 6) |
((DMREAD) << 3) |
((DMREAD) << 0);
d->qpath = Qpalnamesextents;
d->version = 1;
d->mtime = nsec();
d->pdblkno = Bda;
d->pqpath = Qpa;
d->preli = Inle;
d->size = sizeof inle;
strcpy((s8*)d->buf, inle);
putbuf(b, 1);
b = egetmeta(Bda, Bwritable, Bfreshalloc);
settag(b, Tdentry, Qpa);
d = b->d;
d->uid = d->muid = d->gid = -1;
d->mode = DMDIR |
((DMREAD|DMWRITE|DMEXEC) << 6) |
((DMREAD|DMWRITE|DMEXEC) << 3) |
((DMREAD|DMWRITE|DMEXEC) << 0);
d->qpath = Qpa;
d->version = 0;
d->mtime = nsec();
d->pdblkno = Bdroot;
d->pqpath = Qproot;
d->preli = 3;
d->dblocks[0] = Bdanames;
d->dblocks[1] = Bdalnames;
d->dblocks[2] = Bdalnamesextents;
d->dblocks[3] = Bdbkp;
d->dblocks[4] = Bdconfig;
d->dblocks[5] = Bdctl;
d->dblocks[6] = Bdfrees;
d->dblocks[7] = Bdsuper;
d->dblocks[8] = Bdusers;
addname(d, -1, 0, ".n");
addname(d, -1, 1, ".nl");
addname(d, -1, 2, ".nle");
addname(d, -1, 3, "bkp");
addname(d, -1, 4, "config");
addname(d, -1, 5, "ctl");
addname(d, -1, 6, "frees");
addname(d, -1, 7, "super");
addname(d, -1, 8, "users");
putbuf(b, 1);
b = egetmeta(Bdbkpnames, Bwritable, Bfreshalloc);
settag(b, Tdentry, Qpbkpnames);
d = b->d;
d->flags = Fsys|Fn;
d->uid = d->muid = d->gid = -1;
d->mode =
((DMREAD) << 6) |
((DMREAD) << 3) |
((DMREAD) << 0);
d->qpath = Qpbkpnames;
d->version = 1;
d->mtime = nsec();
d->pdblkno = Bdbkp;
d->pqpath = Qpbkp;
d->preli = In;
putbuf(b, 1);
b = egetmeta(Bdbkplnames, Bwritable, Bfreshalloc);
settag(b, Tdentry, Qpbkplnames);
d = b->d;
d->flags = Fsys;
d->uid = d->muid = d->gid = -1;
d->mode =
((DMREAD) << 6) |
((DMREAD) << 3) |
((DMREAD) << 0);
d->qpath = Qpbkplnames;
d->version = 1;
d->mtime = nsec();
d->pdblkno = Bdbkp;
d->pqpath = Qpbkp;
d->preli = Inl;
putbuf(b, 1);
b = egetmeta(Bdbkplnamesextents, Bwritable, Bfreshalloc);
settag(b, Tdentry, Qpbkplnamesextents);
d = b->d;
d->flags = Fsys|Fe;
d->uid = d->muid = d->gid = -1;
d->mode =
((DMREAD) << 6) |
((DMREAD) << 3) |
((DMREAD) << 0);
d->qpath = Qpbkplnamesextents;
d->version = 1;
d->mtime = nsec();
d->pdblkno = Bdbkp;
d->pqpath = Qpbkp;
d->preli = Inle;
d->size = sizeof inle;
strcpy((s8*)d->buf, inle);
putbuf(b, 1);
b = egetmeta(Bdbkp, Bwritable, Bfreshalloc);
settag(b, Tdentry, Qpbkp);
d = b->d;
d->uid = d->muid = d->gid = -1;
d->mode = DMDIR |
((DMREAD|DMWRITE|DMEXEC) << 6) |
((DMREAD|DMWRITE|DMEXEC) << 3) |
((DMREAD|DMWRITE|DMEXEC) << 0);
d->qpath = Qpbkp;
d->version = 0;
d->mtime = nsec();
d->size = strlen(users)+1;
d->pdblkno = Bda;
d->pqpath = Qpa;
d->preli = 3;
d->dblocks[0] = Bdbkpnames;
d->dblocks[1] = Bdbkplnames;
d->dblocks[2] = Bdbkplnamesextents;
d->dblocks[3] = bdconfig0;
d->dblocks[4] = bdroot0;
d->dblocks[5] = bdsuper0;
addname(d, -1, 0, ".n");
addname(d, -1, 1, ".nl");
addname(d, -1, 2, ".nle");
addname(d, -1, 3, "config.0");
addname(d, -1, 4, "root.0");
addname(d, -1, 5, "super.0");
putbuf(b, 1);
b = egetmeta(Bdusersnames, Bwritable, Bfreshalloc);
settag(b, Tdentry, Qpusersnames);
d = b->d;
d->flags = Fsys|Fn;
d->uid = d->muid = d->gid = -1;
d->mode =
((DMREAD) << 6) |
((DMREAD) << 3) |
((DMREAD) << 0);
d->qpath = Qpusersnames;
d->version = 1;
d->mtime = nsec();
d->pdblkno = Bdusers;
d->pqpath = Qpusers;
d->preli = In;
putbuf(b, 1);
b = egetmeta(Bduserslnames, Bwritable, Bfreshalloc);
settag(b, Tdentry, Qpuserslnames);
d = b->d;
d->flags = Fsys;
d->uid = d->muid = d->gid = -1;
d->mode =
((DMREAD) << 6) |
((DMREAD) << 3) |
((DMREAD) << 0);
d->qpath = Qpuserslnames;
d->version = 1;
d->mtime = nsec();
d->pdblkno = Bdusers;
d->pqpath = Qpusers;
d->preli = Inl;
putbuf(b, 1);
b = egetmeta(Bduserslnamesextents, Bwritable, Bfreshalloc);
settag(b, Tdentry, Qpuserslnamesextents);
d = b->d;
d->flags = Fsys|Fe;
d->uid = d->muid = d->gid = -1;
d->mode =
((DMREAD) << 6) |
((DMREAD) << 3) |
((DMREAD) << 0);
d->qpath = Qpuserslnamesextents;
d->version = 1;
d->mtime = nsec();
d->pdblkno = Bdusers;
d->pqpath = Qpusers;
d->preli = Inle;
d->size = sizeof inle;
strcpy((s8*)d->buf, inle);
putbuf(b, 1);
b = egetmeta(Bdusers, Bwritable, Bfreshalloc);
settag(b, Tdentry, Qpusers);
d = b->d;
d->uid = d->muid = d->gid = -1;
d->mode = DMDIR |
((DMREAD|DMWRITE|DMEXEC) << 6) |
((DMREAD|DMWRITE|DMEXEC) << 3) |
((DMREAD|DMWRITE|DMEXEC) << 0);
d->qpath = Qpusers;
d->version = 1;
d->mtime = nsec();
d->pdblkno = Bda;
d->pqpath = Qpa;
d->preli = 8;
d->dblocks[0] = Bdusersnames;
d->dblocks[1] = Bduserslnames;
d->dblocks[2] = Bduserslnamesextents;
d->dblocks[3] = Bdusersinuse;
d->dblocks[4] = Bdusersstaging;
addname(d, -1, 0, ".n");
addname(d, -1, 1, ".nl");
addname(d, -1, 2, ".nle");
addname(d, -1, 3, "inuse");
addname(d, -1, 4, "staging");
putbuf(b, 1);
b = egetmeta(Bdusersinuse, Bwritable, Bfreshalloc);
settag(b, Tdentry, Qpusersinuse);
d = b->d;
d->uid = d->muid = d->gid = -1;
d->mode =
((DMREAD) << 6) |
((DMREAD) << 3) |
((DMREAD) << 0);
d->qpath = Qpusersinuse;
d->version = 1;
d->mtime = nsec();
d->size = userslen;
d->pdblkno = Bdusers;
d->pqpath = Qpusers;
d->preli = 3;
strcpy((s8*)d->buf, users);
putbuf(b, 1);
b = egetmeta(Bdconfig, Bwritable, Bfreshalloc);
settag(b, Tdentry, Qpconfig);
d = b->d;
d->uid = d->muid = d->gid = -1;
d->mode =
((DMREAD) << 6) |
((DMREAD) << 3) |
((DMREAD) << 0);
d->qpath = Qpconfig;
d->version = 1;
d->mtime = nsec();
memset(cbuf, 0, Ddatasize);
d->size = configstr(cbuf, Ddatasize);
d->pdblkno = Bda;
d->pqpath = Qpa;
d->preli = 4;
strncpy((s8*)d->buf, cbuf, d->size);
putbuf(b, 1);
reamfile(Bdctl, Qpctl, "ctl", 0, Bda, Qpa, 5, 0);
reamfile(Bdfrees, Qpfrees, "frees", 0, Bda, Qpa, 6, Fe);
reamfile(Bdusersstaging, Qpusersstaging, "staging",
0, Bdusers, Qpusers, 4, 0);
}
void
superream(u64 size, u64 nblocks)
{
Iobuf *sbuf;
Dentry *s;
sbuf = getbuf(Bdsuper, 1, Bwritable, Bfreshalloc, getcallerpc(&size));
settag(sbuf, Tdentry, Qpsuper);
s = sbuf->d;
s->uid = s->muid = s->gid = -1;
s->mode =
((DMREAD) << 6) |
((DMREAD) << 3) |
((DMREAD) << 0);
s->qpath = Qpsuper;
s->version = 1;
s->mtime = nsec();
s->size = sizeof(Super);
s->pdblkno = Bda;
s->pqpath = Qpa;
s->preli = 7;
s->qidgen = Nqidgen;
s->fsok = 1;
/* not bothering to ream the backup blocks,
they will be overwritten almost immediately anyway */
config.size = size;
config.nblocks = nblocks;
config.config.dest[0] = nblocks-Bdconfig;
config.super.dest[0] = nblocks-Bdsuper;
config.root.dest[0] = nblocks-3;
/* this will enable backups */
config.config.srcbno = Bdconfig;
config.super.srcbno = Bdsuper;
config.root.srcbno = Bdroot;
strncpy(config.service, service, Servicelen);
reamfile(config.config.dest[0], Qpconfig0, "config.0",
0, Bdbkp, Qpbkp, 3, 0);
reamfile(config.root.dest[0], Qproot0, "root.0",
0, Bdbkp, Qpbkp, 4, 0);
reamfile(config.super.dest[0], Qpsuper0, "super.0",
0, Bdbkp, Qpbkp, 5, 0);
putbuf(sbuf, 1);
if(chatty9p > 1)
dprint("backup config %llud"
" super %llud"
" root %llud\n",
config.config.dest[0],
config.super.dest[0],
config.root.dest[0]);
reamdefaults(config.config.dest[0], config.super.dest[0], config.root.dest[0]);
if(config.root.dest[0]-Nbused > 0)
ufree(&frees, Nbused, config.root.dest[0]-Nbused);
else if (config.root.dest[0] == Nbused)
dprint("mafs: %s no free blocks: config.root.dest[0] %llud Nbused %ud Nminblocks %llud\n",
service, config.root.dest[0], Nbused, Nminblocks);
else
panic("not enough blocks for mafs config.root.dest[0] %llud Nbused %ud Nminblocks %d\n",
config.root.dest[0], Nbused, Nminblocks);
if(chatty9p > 1)
showextents(2, "free extents: ", &frees);
if(chatty9p > 1)
dprint("done\n");
fsok(0);
}
/*
open the dev file OEXCL?
cannot do exclusive use file as the fd could get invalid
if no I/O is done for an extended period.
*/
void
ream(u64 size)
{
char buf[Blocksize];
int i;
u64 nblocks;
nblocks = size/Blocksize;
if(nblocks < Nminblocks)
panic("not enough space");
if(chatty9p > 1){
dprint("%s %s ream %llud bytes into %llud blocks of %d bytes\n",
service, devfile, size, nblocks, Blocksize);
dprint(" (data block size: usable %d bytes)\n",
Maxdatablocksize);
dprint(" (name length: %d bytes)\n", Servicelen);
}
memset(buf, 0, Blocksize);
for(i = 0; i < Nbused; i++)
devwrite(i, buf, 1);
superream(size, nblocks);
fsok(1);
}
/*
* init the devices
* wipe some of the file systems, or all if ream is set
* this code really assumes that only one file system exists
*/
void
init(int doream, u64 size)
{
u32 unitsize;
Iobuf *sb, *b;
Dentry *s;
s8 *rptr;
if(doream)
ream(size);
else{
initconfig(Bdconfig);
loadfrees();
}
/* check magic */
b = egetmetachk(Bdmagic, Breadonly, Tdentry, Qpmagic);
if(waserror()){
putbuf(b, 0);
nexterror();
}
if(strncmp((s8*)b->d->buf,magic,strlen(magic)) != 0){
print("init: bad magic -%s-", (s8*)b->io+256);
panic("bad magic");
}
unitsize = strtoul((s8*)b->d->buf+strlen(magic), &rptr, 10);
if(unitsize != Blocksize){
print("init incorrect block size Blocksize %llud unitsize %d\n",
Blocksize, unitsize);
panic("bad Blocksize != unitsize");
}
poperror();
putbuf(b, 0);
/* check super */
sb = egetmetachk(Bdsuper, Bwritable, Tdentry, Qpsuper);
s = sb->d;
if(config.size != size){
dprint("corrupted disk or disk size changed:"
" config.size %llud size %llud\n"
"This is an unrecoverable situation."
" Ream the disk and start over.\n",
config.size, size);
panic(errstring[Edirty]);
}
if(s->fsok != 1){
panic("There was an unsafe shutdown:\n"
" use \'disk/fsck %s\' to check the disk state.\n"
" Or, use \'disk/fsok %s\' to flip the fsok flag.\n",
devfile, devfile);
panic(errstring[Edirty]);
}
s->fsok = 0;
putbuf(sb, 1);
shuttingdown = 0;
if(doream == 0)
clearfrees();
usersinit();
}
/*
* returns 1 if n is prime
* used for adjusting lengths
* of hashing things.
* there is no need to be clever
*/
int
prime(long n)
{
long i;
if((n%2) == 0)
return 0;
for(i=3;; i+=2) {
if((n%i) == 0)
return 0;
if(i*i >= n)
return 1;
}
}
void
hexdump(void *a, int n)
{
char s1[30], s2[4];
uchar *p;
int i;
p = a;
s1[0] = 0;
for(i=0; i<n; i++) {
sprint(s2, " %.2ux", p[i]);
strcat(s1, s2);
if((i&7) == 7) {
print("%s\n", s1);
s1[0] = 0;
}
}
if(s1[0])
print("%s\n", s1);
}