#include<iostream>

using namespace std;

long factorial(int n);

int main()
{
	int n(0);
	cin>>n;
	long val=factorial(n);
	cout<<val;
	cin.get();
	return 0;
}

long factorial(int n)
{
	long result(1);
	//	while(n--)
	//	{
	//		result*=n;
	//	}
	while(n>0) //doesn't let n reach 0
	{
		result*=n;
		n--;//decrements only after the evaluation
	}
	return result;
}