#include <stdio.h>
#include <stdlib.h>

int factorial (int n)
{
	if(n==0)
		return 1;
	else
		return n*factorial(n-1);
}

int main(int argc, char* argv[])
{
	int n;
	printf("input n: ");
	scanf("%d",&n);
	printf("%d",factorial(n));
	system("pause");
	return 0;
}