题解 | 牛牛学数列4

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextInt()) { // 注意 while 处理多个 case
            int n = in.nextInt();
            int total = 0;
            for(int i = 1; i <= n; i++){
                total += sum(i);
            }
            System.out.print(total);
        }
    }
    public static int sum(int i){
        int s = 0;
        for(int j = 1; j <= i; j++){
            s = s + j;
        }
        return s;
    }
}