/in/foo.cc: In function 'int main()':
/in/foo.cc:12:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
      for(i = 0;i < strlen(a1);i++){
                  ^
/in/foo.cc:14:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
       for(j = 0;j < strlen(a2);j++){
                   ^
/in/foo.cc:10:20: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
      scanf("%s",a2);
                    ^