/in/foo.cc: In function 'int main()':
/in/foo.cc:15:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<s.length();i++)
                 ~^~~~~~~~~~~
/in/foo.cc:17:11: warning: 'ans' may be used uninitialized in this function [-Wmaybe-uninitialized]
     if(ans%3==0) cout<<1<<endl;
        ~~~^~