/in/foo.cc: In function 'int main()':
/in/foo.cc:5:2: error: 'cin' was not declared in this scope
  cin>>a;
  ^~~
/in/foo.cc:6:2: error: 'cout' was not declared in this scope
  cout<<fixed<<setprecision(12)<<a<<endl;
  ^~~~
/in/foo.cc:6:36: error: 'endl' was not declared in this scope
  cout<<fixed<<setprecision(12)<<a<<endl;
                                    ^~~~