HDU 1001

陈小盈 2022-07-22

Sum Problem

Time Limit: 1000/500 MS (Java/Others)

Memory Limit: 65536/32768 K (Java/Others)

Problem Description

Hey, welcome to HDOJ(Hangzhou Dianzi University Online Judge).
In this problem, your task is to calculate SUM(n) = 1 + 2 + 3 + … + n.

Input

The input will consist of a series of integers n, one integer per line.

Output

For each case, output SUM(n) in one line, followed by a blank line. You may assume the result will be in the range of 32-bit signed integer.

Sample Input

1
100

###Sample Output

1

5050

Author

DOOM III

Java

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//package com.ccying.oj.hdu;

import java.util.Scanner;

/**
 * <h2>Sum Problem.</h2>
 *
 * @author ccying
 * @since 2022/7/20
 */
public class Main{
    public static void main(String[] args) {
        Scanner cin = new Scanner(System.in);
        while (cin.hasNext()) {
            long n = cin.nextLong();
            long a1 = 1L;
            long sum = n * (a1 + n) / 2;   // 等差数列求和
            System.out.println(sum);
            System.out.println();
        }
    }
}
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HDU 1000