/in/foo.cc: In function 'int main()':
/in/foo.cc:10:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i=0;i<s.length();++i)
               ~^~~~~~~~~~~
/in/foo.cc:15:16: 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]
  cout<<ans;
           ^