hdu 1001 Sum Problem

//You may assume the result will be in the range of 32-bitsigned integer.

#include"iostream"

#include"stdio.h"

#include"algorithm"

using namespace std;

int main()

{

int n,sum;

while(scanf("%d",&n)!=EOF)

{

//printf("%d\n\n",(1+n)*n/2); //可能n^2会溢出

if(n%2==0)

          sum=n/2*(n+1);

       else

          sum=(n+1)/2*n; 

          

       printf("%d\n\n",sum);

}

   getchar();getchar();

    return 0;

}