foo.c: In function 'main':
foo.c:3:2: error: 'cout' undeclared (first use in this function)
  cout<<"   A   "<<endl;
  ^~~~
foo.c:3:2: note: each undeclared identifier is reported only once for each function it appears in
foo.c:3:19: error: 'endl' undeclared (first use in this function)
  cout<<"   A   "<<endl;
                   ^~~~

[Hydro](https://hydro.ac)提供评测服务