using System;

class LukavaSuma {
  static void Main() {
    int n, k, i, sum;
    Console.WriteLine("Unesi n");
    n = int.Parse(Console.ReadLine());
    sum = 1;
    k = 1;
    for(i = 2; i <= n; i++) {
      k *= i;
      sum += k;
    }
    Console.WriteLine("Suma -> {0}", sum);
  }
}