#include<iostream>
#include<algorithm>
#include<vector>
#include<stack>
#include<queue>
#include<cstdio>
#include<climits>
#include<cmath>
#include<cstring>
#include<string>
#include<complex>
#include<iomanip>

#define EPS (1e-10)
using namespace std;
#define PI (3.1415926535)

int f(int n){
	if(n == 1)return 1;
	return n*f(n-1);
}

int main(){
	int n;
	cin >> n;
	if(n == 20){
		cout << f(19)*2 << '0' <<  endl;
	}else{
		cout << f(n) << endl;
	}

	return 0;
}