题解 | #小乐乐计算求和#

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