/in/foo.cc: In function 'int main()':
/in/foo.cc:18:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<in.size();i++) a.push_back(in[i]-'0');
              ~^~~~~~~~~~
/in/foo.cc:22:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0;i<a.size();i++){
               ~^~~~~~~~~
/in/foo.cc:26:9: warning: value computed is not used [-Wunused-value]
     c[i]-n;