nyoj436sum 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

 
#include<stdio.h>
int main()
{
    int n;
    while(scanf("%d",&n)!=EOF)
    {
        if(n>0)printf("%d\n",n*(n+1)/2);
        if(n<=0)
            {
                n=-n;printf("%d\n",-n*(n+1)/2+1);
            }
    }
    return 0;
}
        

来源