#include <iostream>
using namespace std;

int main ()
{
	float a;
	cout<<"Nhap diem trung binh: ";
	cin>>a;

	while(a<0||a>10)

	{cout<<"nhap lai a "<<endl;
	cin>>a;}

	if (a<5) cout<<"KHONG DAT"<<endl;
	if (a>=5&&a<6.5)	cout<<"DAT"<<endl;
 	if(a>=6.5&&a<=7.9)	cout<<"KHA"<<endl;
 	if(a>=8.0)	cout<<"GIOI"<<endl;

 	return 0;
}