/in/foo.cc: In function 'void sol()':
/in/foo.cc:9:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0; i<s.size(); i++) ans+=(s[i]-'0');
               ~^~~~~~~~~
/in/foo.cc:15:9: error: return-statement with a value, in function returning 'void' [-fpermissive]
  return 0;
         ^