// editor10
import java.util.*;
public class Main{
    public static void main(String[] args)
    {
        Scanner sc=new Scanner(System.in);
        int n=sc.nextInt();
        if(n<=0)
        {
            System.out.print("Invalid input");
            return;
        }
        else
        {
        int fact=1;
        for(int i=n;i>=1;i--)
        {
            fact=fact*i;
            
        }
        }
        System.out.print(fact);
    }
}