一个求1到n的和的题：
我代码如下：
#include<iostream>
using namespace std;
int main()
{
    unsigned int n;//为什么用long就不行了？
    while(cin>>n)
    {
        cout<<(1+n)*n/2<<endl<<endl;
    }
    return 0;
}
代码第五行把unsigned换成long为何就不行了？

哥们！有想法的就发表下咯！

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

原题是这样的！

我也觉得呗！