/in/foo.cc: In function 'int main(int, const char**)':
/in/foo.cc:21:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i=0;i<strlen(a);i++)
                      ^
/in/foo.cc:34:11: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     if(sum==strlen(a))
           ^
/in/foo.cc:9:9: warning: unused variable 'len' [-Wunused-variable]
     int len;
         ^