#include <stdio.h>
#include <conio.h>
#include <Windows.h>

/*
 cu cho nguoi dung nhap lien tuc vao cac so den khi nao nguoi dung khong nhap nua thi thoi
 luc nay se tinh ra tong giai thua cac so ma nguoi dung da nhap. 
*/

void nhap(int &);
int tinhgiaithua(int n);

void nhap(int &n)
{
	do
	{
		printf("\nhay nhap vao so nguyen duong n : ");
		scanf("%d",&n);
		if (n <= 0)
		{
			printf("\ngia tri khong hop le , xin kiem tra lai");
		}
	} while (n <= 0);
}
int tinhgiaithua(int n)
{
	int tich = 1;
	for (int i = 2; i <= n; i++)
	{
		tich *= i;
	}
	return tich;
}


int main()
{     
	int tong = 0;
	while (true)
	{
		printf("\n-------------MENU---------\n");
		printf("\n1.nhap");
		printf("\n2.thoat");

		int luachon;
		nhap:
		printf("\nMoi ban nhap vao lua chon : ");
		scanf("%d",&luachon);
		
		if(luachon != 1 && luachon != 2)
		{
		    printf("\nLua chon khong hop le! xin hay nhap lai cam on ");
			
		}
		if(luachon == 1)
		{  
			system("cls");
		    int n;
			nhap(n);
			tong += tinhgiaithua(n);
		}
		else
		{
		
			printf("\nTong = %d",tong);
			break;
		}
	}


	getch();
	return 0;



}