/in/foo.cc: In function 'int main()':
/in/foo.cc:7:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<s.size();i++)
              ~^~~~~~~~~
/in/foo.cc:10:9: warning: 'n' may be used uninitialized in this function [-Wmaybe-uninitialized]
  cout<<n;
         ^