sum of all integer numbers（坑題，水題）

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

輸入

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

輸出

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

樣例輸入

3

樣例輸出

6

#include<iostream>
#include<string.h>
#include<stdio.h>
#include<ctype.h>
#include<algorithm>
#include<stack>
#include<queue>
#include<set>
#include<math.h>
#include<vector>
#include<deque>
#include<list>
using namespace std;
int main()
{
    int n;
    //int sum=0;
    while(scanf("%d",&n)!=EOF)
    {
        printf("%d\n", (abs(n - 1) + 1) * (1 + n) / 2);
    }
    return 0;
}