import java.math.BigInteger;
import java.util.Scanner;

public class B2 {
    final static int N = 1977;

    public static void main(String[] args) {
        BigInteger s = BigInteger.ONE;
        for (int i = 2; i <= N; i++)
            s = s.multiply(new BigInteger(String.valueOf(i)));
        System.out.println(s);
        cin.close();
    }

    static Scanner cin = new Scanner(System.in);
}