#include<stdio.h>
int main()
{
    
    	
	int fun (int x);
	int n;
	scanf("%d",&n);
	printf("%d",fun(n));
	return 0;
 } 
 int fun (int x)
 {
    
    
	if(x==0)
		return 1;
				
 	return x*fun(x-1);
 	
 }