#include <iostream>
using namespace std;
int main(){
	int n, ans;
	cin >> n;
	ans = (1 + n) * (n + 1) / 4;
	cout <<ans;
}
/**************************************************************
	Problem: 1003
	User: long
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/