题解 | 牛牛学数列4

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
  	//用BufferedReader确实提高了效率
    static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    public static void main(String[] args) throws IOException {
        int a = Integer.valueOf(br.readLine());
        //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 a = in.nextInt();
            long sum = 1;
            for(int i = 2; i <= a; i++) {
                int temp = 0;
                for(int j = 1; j <= i; j++) {
                    temp += j;
                }
                sum += temp;   
            }
            System.out.println(sum);
        //}
    }
}