hdoj1001

1到n之和

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