foo.c: In function 'zfc':
foo.c:12:5: warning: array subscript has type 'char' [-Wchar-subscripts]
    a[s[i]]++;
     ^
foo.c: In function 'main':
foo.c:36:2: 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:36:2: warning: ignoring return value of 'gets', declared with attribute warn_unused_result [-Wunused-result]
  gets(s);
  ^~~~~~~
/tmp/ccsQromJ.o: In function `main':
foo.c:(.text.startup+0x2c): warning: the `gets' function is dangerous and should not be used.

[Hydro](https://hydro.ac)提供评测服务