HDOJ_1001_Sum Problem

题目：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

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这个题目逻辑、编程都是没有什么问题的，但是有几个小坑。

1.要看清输出格式，每一行下面需要空一行，还有就是

2.n的类型，应为double，我一开始是int型，怎么也不能AC。

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代码如下：

#include<iostream>using namespace std;int main(){    double n;    while(cin>>n){        cout<<(int)((1+n)*n/2)<<endl<<endl;    }}