#include <iostream>
using namespace std;

#include <conio.h>

int main()
{
	BatDau:

	int n;
	cout << "\nNhap n: ";		cin >> n;
	int S = 0;
	for(int i =  1; i <= n; ++i)
	{
		S += i;
	}
	cout << "KQ = " << S;

	cout << "\nNhap y de kiem tra lai:";
	char y = getch();
	if(y == 'Y' || y == 'y')
	{
		system("cls");
		goto BatDau;
	}

	system("pause");
	return 0;
}