/in/foo.cc: In function 'int main()':
/in/foo.cc:7:2: error: 'cout' was not declared in this scope
  cout<<setiosflags(ios::fixed)<<setprecision(2);
  ^~~~
/in/foo.cc:7:20: error: incomplete type 'std::ios {aka std::basic_ios<char>}' used in nested name specifier
  cout<<setiosflags(ios::fixed)<<setprecision(2);
                    ^~~
/in/foo.cc:8:2: error: 'cin' was not declared in this scope
  cin>>danjia;
  ^~~