sum of all integer numbers

sum of all integer numbers

时间限制：1000 ms  |  内存限制：65535 KB

难度：0

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

代码实现：（注意要区分n大于0和小于0的情况）

#include<stdio.h>
int main()
{
    int n;
    long i,sum;
    while(scanf("%d",&n)!=EOF)
    {
        sum=0;
        if(n>0)
        {
            for(i=1;i<=n;i++)
                sum+=i;
        }
        else
        {
            for(i=1;i>=n;i--)
                sum+=i;    
        }
        printf("%d\n",sum);
    }
    return 0;
}