#include<fstream>
#include<iostream>
using namespace std;
int a;
int factorial(int n) {
	if ((n==0)||(n==1))  return 1;
	else return factorial(n-1)*n;
}
int main() {
	ifstream f("fact.in");
	ofstream g("fact.out");
	f>>a;
	g<<factorial(a);
	return 0;
}