题目描述
Hey, welcome to ahstu oj.
In this problem, your task is to calculate SUM(n) = 1 + 2 + 3 + … + n.
输入
The input will consist of a series of integers n, one integer per line.
输出
For each case, output SUM(n) in one line. You may assume the result will be in the range of 32-bit signed integer.
#include<bits/stdc++.h>
int main(){
int n;
while(scanf(“%d”,&n)!=EOF){cout<<(1+n)*n/2<<endl;}
return 0;
}