foo.c: In function 'main':
foo.c:7:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
  gets(s);
  ^~~~
In file included from /usr/include/stdio.h:862:0,
                 from foo.c:1:
/usr/include/x86_64-linux-gnu/bits/stdio2.h:232:1: note: declared here
 gets (char *__str)
 ^~~~
foo.c:9:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
  gets(c);
  ^~~~
In file included from /usr/include/stdio.h:862:0,
                 from foo.c:1:
/usr/include/x86_64-linux-gnu/bits/stdio2.h:232:1: note: declared here
 gets (char *__str)
 ^~~~
foo.c:13:3: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
   for(j=0;c[j]!=0;j++)
   ^~~
foo.c:16:4: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'for'
    if(n==0)
    ^~
foo.c:7:2: warning: ignoring return value of 'gets', declared with attribute warn_unused_result [-Wunused-result]
  gets(s);
  ^~~~~~~
foo.c:9:2: warning: ignoring return value of 'gets', declared with attribute warn_unused_result [-Wunused-result]
  gets(c);
  ^~~~~~~
/tmp/ccMMDQGG.o: In function `main':
foo.c:(.text.startup+0x31): warning: the `gets' function is dangerous and should not be used.