HDU1001 Sum Problem

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

代码

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