using System;
public class Program
{
static int giaiThua(int n) {
int rs = 1;
for (int i = 1; i <= n; i++) {
rs *= i;
}
return rs;
public static void Main()
Console.WriteLine("Nhap N giai thua:");
int n = int.Parse(Console.ReadLine());
Console.WriteLine(giaiThua(n));