//C语言递归：输入整数n，求n的阶乘

//C语言递归：输入整数n，求n的阶乘
#include<stdio.h>
int fac(int x)
{
	if (x > 1)
		return x * fac(x-1);
	else
		return 1;

}



int main()
{
	int n;
	scanf_s("%d", &n);
	printf("%d", fac(n));
	return 0;
}