HDU 1001 求n项和

HDU 1001 Sum Problem 2019.3.21.2

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

#include<iostream>
using namespace std;
int main()
{
  int n,i;
  while(cin>>n){
    int sum=0;
    for(i=1;i<=n;i++){
        sum+=i;
    }
  cout<<sum<<endl;
  cout<<endl;
  }
  return 0;
}

总结
这道题有三个地方需要注意。
第一，sum=0的位置是放在while循环里面，还是放在外面？
第二，输出格式里有一行空白，怎么实现空白行的输出呢？
第三，空白行的位置是放在sum结果后，还是放在结果之前呢？