package com.javarush.task.task15.task1531;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.math.BigInteger;
/*
Факториал
*/
public class Solution {
public static void main(String[] args) throws IOException {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
int input = Integer.parseInt(reader.readLine());
reader.close();
System.out.println(factorial(input));
}
public static String factorial(int n) {
double result = 1;
if (n >= 0) {
for (int i = 1; i <= n; i++) {
result = result * i;
}
} else result = 0;
return String.valueOf((BigInteger.valueOf((long) result)));
}
}