import java.util.Scanner; public class Main{ public static void main(String[]args){ Scanner sc = new Scanner(System.in); int n = sc.nextInt(); int sum = 0; for(int i = 1; i <= n; i++){ sum += fac(i); } System.out.println(sum); } public static int fac(int n){ if(n == 1 || n == 0){ return 1; }else{ return n * fac(n - 1); } } }