package com.njupt.acm;
import java.math.BigInteger;
import java.util.Scanner;
public class UVA_10497 {
public static void main(String[] args) {
BigInteger d[] = new BigInteger[805];
d[1] = new BigInteger("0");
d[2] = new BigInteger("1");
int i;
for(i = 3 ; i <= 801 ; ++i){
d[i] = new BigInteger((i - 1) + "").multiply(d[i-2].add(d[i-1]));
}
Scanner scanner = new Scanner(System.in);
int n ;
while(true){
n = scanner.nextInt();
if(n < 0){
break;
}
System.out.println(d[n]);
}
}
}