import java.math.BigInteger;

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {

        Scanner sc=new Scanner(System.in);

        int n=sc.nextInt();

        BigInteger ans=fac(n);

        System.out.println(ans);

    }

    public static BigInteger fac(int n){

        BigInteger res=BigInteger.valueOf(n);

        while(--n>1) res=res.multiply(BigInteger.valueOf(n));

        return res;

    }

}