/in/foo.c: In function 'main':
/in/foo.c:20:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
  gets(s1);
  ^~~~
In file included from /in/foo.c:1:0:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.c:21:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
  gets(s2);
  ^~~~
In file included from /in/foo.c:1:0:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.c: In function 'diff':
/in/foo.c:13:9: warning: 'n' may be used uninitialized in this function [-Wmaybe-uninitialized]
  return n;
         ^
/in/foo.c: In function 'main':
/in/foo.c:24:2: warning: 'n' may be used uninitialized in this function [-Wmaybe-uninitialized]
  printf("%d %d",l1,l2);
  ^~~~~~~~~~~~~~~~~~~~~
/in/foo.c:24:2: warning: 'n' may be used uninitialized in this function [-Wmaybe-uninitialized]
/tmp/ccRaYhl0.o: In function `main':
foo.c:(.text.startup+0x19): warning: the `gets' function is dangerous and should not be used.