HDU 1214 圆桌会议

#include <iostream>
#include <algorithm>
#include <cstring>
using namespace std;
int main()
{
	int i,j,k;
	while(cin>>i){
		j=i/2;
		k=i-j;
		cout<<j*(j-1)/2+k*(k-1)/2<<endl;
	} 
	return 0;
 }