Sum Problem

Time Limit: 1000/500 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)Total Submission(s): 637240 Accepted Submission(s): 161358

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

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Accepted Code

package cn.edu.hdu.acm;

import java.util.Scanner;

public class Main1001 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while(scanner.hasNext()){
            int n = scanner.nextInt();
            if(n % 2 == 0){
                int sum = n/2 * (n + 1);
                System.out.println(sum);
                System.out.println();
            }else{
                int sum = (n + 1) /2 *n;
                System.out.println(sum);
                System.out.println();
            }
        }
    }
}