ACM-sum of all integer numbers

描述

Your task is to find the sum of all integer numbers lying between 1 and N inclusive.

输入

There are multiple test cases.
The input consists of a single integer N that is not greater than 10000 by it's absolute value.

输出

Write a single integer number that is the sum of all integer numbers lying between 1 and N inclusive.

样例输入

3

样例输出

6

代码：

01.#include<iostream>

02.usingnamespace std;

03.#include <stdio.h>

04.intmain()

05.{

06.intn;

07.intt;

08.while(scanf("%d",&n)==1)

09.{

10.if(n > 0)

11.printf("%d\n",(1+n)*n/2);

12.elseif(n ==0)

13.printf("%d\n",1);

14.else

15.{

16.t = -n;

17.printf("%d\n",-(1+t)*t/2+1);

18.}

19.}

20. 

21.return0;

22.}