HDOJ 1001
#include <iostream>
using namespace std;
int main()
{
int n;
while(cin>>n)
{
if(n%2==0)
cout<<(n/2*(n+1))<<endl<<endl;
else if(n%2==1)
cout<<(n+1)/2*n<<endl<<endl;
}
return 0;
}
一个小陷阱