题解 | #牛牛学数列4#

import java.util.*;

public class Main{
    public static void main(String[] args)throws Exception{
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
           System.out.println(sum(n));
    }
    
    public static int sum(int n){
        int sum = 0;
        int sum_total = 0;
       for(int i = 1; i <= n; i++){
          sum += i;
          sum_total += sum;
       }
        return sum_total;
    }
}