/in/foo.c: In function 'main':
/in/foo.c:5:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
  gets(s);
  ^~~~
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:7:2: warning: 'gets' is deprecated [-Wdeprecated-declarations]
  gets(t);
  ^~~~
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:11:4: warning: array subscript has type 'char' [-Wchar-subscripts]
   a[t[i]]++;
    ^
/in/foo.c:14:8: warning: array subscript has type 'char' [-Wchar-subscripts]
   if (a[s[i]] == 0)
        ^
/tmp/ccm6uuHz.o: In function `main':
foo.c:(.text.startup+0x1a): warning: the `gets' function is dangerous and should not be used.