/in/foo.cc: In function 'int main()':
/in/foo.cc:8:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i=0;i<strlen(s);i++)
                      ^
/in/foo.cc:10:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             for(int j=0;j<strlen(s);j++)
                          ^