/in/foo.cc: In function 'int main()':
/in/foo.cc:13:2: error: incomplete type 'std::ios {aka std::basic_ios<char>}' used in nested name specifier
  ios::sync_with_stdio(false);
  ^~~
/in/foo.cc:14:2: error: 'cin' was not declared in this scope
  cin>>x0>>yo;
  ^~~
/in/foo.cc:22:2: error: 'cout' was not declared in this scope
  cout<<cnt;
  ^~~~