Language: C++

#include<algorithm>
#include<map>
#include<stack>
#include<string>
#include<set>
using namespace std;
int main(){
	int x;
	cin >> x;
	if (x >= 400 && x <= 599)cout << 8 << endl;
	else if (x >= 600 && x <= 799)cout << 7 << endl;
	else if (x >= 800 && x <= 999)cout << 6 << endl;
	else if (x >= 1000 && x <= 1199)cout << 5 << endl;
	else if (x >= 1200 && x <= 1399)cout << 4 << endl;
	else if (x >= 1400 && x <= 1599)cout << 3<< endl;
	else if (x >= 1600 && x <= 1799)cout << 2<< endl;
	else if (x >= 1800 && x <= 1999)cout << 1 << endl;
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:9:9: error: 'cin' was not declared in this scope
    9 |         cin >> x;
      |         ^~~
a.cc:6:1: note: 'std::cin' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
    5 | #include<set>
  +++ |+#include <iostream>
    6 | using namespace std;
a.cc:10:34: error: 'cout' was not declared in this scope
   10 |         if (x >= 400 && x <= 599)cout << 8 << endl;
      |                                  ^~~~
a.cc:10:34: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:10:47: error: 'endl' was not declared in this scope
   10 |         if (x >= 400 && x <= 599)cout << 8 << endl;
      |                                               ^~~~
a.cc:6:1: note: 'std::endl' is defined in header '<ostream>'; this is probably fixable by adding '#include <ostream>'
    5 | #include<set>
  +++ |+#include <ostream>
    6 | using namespace std;
a.cc:11:39: error: 'cout' was not declared in this scope
   11 |         else if (x >= 600 && x <= 799)cout << 7 << endl;
      |                                       ^~~~
a.cc:11:39: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:11:52: error: 'endl' was not declared in this scope
   11 |         else if (x >= 600 && x <= 799)cout << 7 << endl;
      |                                                    ^~~~
a.cc:11:52: note: 'std::endl' is defined in header '<ostream>'; this is probably fixable by adding '#include <ostream>'
a.cc:12:39: error: 'cout' was not declared in this scope
   12 |         else if (x >= 800 && x <= 999)cout << 6 << endl;
      |                                       ^~~~
a.cc:12:39: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:12:52: error: 'endl' was not declared in this scope
   12 |         else if (x >= 800 && x <= 999)cout << 6 << endl;
      |                                                    ^~~~
a.cc:12:52: note: 'std::endl' is defined in header '<ostream>'; this is probably fixable by adding '#include <ostream>'
a.cc:13:41: error: 'cout' was not declared in this scope
   13 |         else if (x >= 1000 && x <= 1199)cout << 5 << endl;
      |                                         ^~~~
a.cc:13:41: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:13:54: error: 'endl' was not declared in this scope
   13 |         else if (x >= 1000 && x <= 1199)cout << 5 << endl;
      |                                                      ^~~~
a.cc:13:54: note: 'std::endl' is defined in header '<ostream>'; this is probably fixable by adding '#include <ostream>'
a.cc:14:41: error: 'cout' was not declared in this scope
   14 |         else if (x >= 1200 && x <= 1399)cout << 4 << endl;
      |                                         ^~~~
a.cc:14:41: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:14:54: error: 'endl' was not declared in this scope
   14 |         else if (x >= 1200 && x <= 1399)cout << 4 << endl;
      |                                                      ^~~~
a.cc:14:54: note: 'std::endl' is defined in header '<ostream>'; this is probably fixable by adding '#include <ostream>'
a.cc:15:41: error: 'cout' was not declared in this scope
   15 |         else if (x >= 1400 && x <= 1599)cout << 3<< endl;
      |                                         ^~~~
a.cc:15:41: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:15:53: error: 'endl' was not declared in this scope
   15 |         else if (x >= 1400 && x <= 1599)cout << 3<< endl;
      |                                                     ^~~~
a.cc:15:53: note: 'std::endl' is defined in header '<ostream>'; this is probably fixable by adding '#include <ostream>'
a.cc:16:41: error: 'cout' was not declared in this scope
   16 |         else if (x >= 1600 && x <= 1799)cout << 2<< endl;
      |                                         ^~~~
a.cc:16:41: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:16:53: error: 'endl' was not declared in this scope
   16 |         else if (x >= 1600 && x <= 1799)cout << 2<< endl;
      |                                                     ^~~~
a.cc:16:53: note: 'std::endl' is defined in header '<ostream>'; this is probably fixable by adding '#include <ostream>'
a.cc:17:41: error: 'cout' was not declared in this scope
   17 |         else if (x >= 1800 && x <= 1999)cout << 1 << endl;
      |                                         ^~~~
a.cc:17:41: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:17:54: error: 'endl' was not declared in this scope
   17 |         else if (x >= 1800 && x <= 1999)cout << 1 << endl;
      |                                                      ^~~~
a.cc:17:54: note: 'std::endl' is defined in header '<ostream>'; this is probably fixable by adding '#include <ostream>'