/in/foo.cc: In function 'int main()':
/in/foo.cc:14:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0;i<strlen(s1);i++)
                ^
/in/foo.cc:19:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int j=0;j<strlen(s2);j++)
                  ^