#include <bits/stdc++.h>

using namespace std;

int main() {
//	freopen("date.in", "r", stdin);
//	freopen("date.out","w", stdout);
	cin.sync_with_stdio(false);
	
	int N;
	cin >> N;
	long long sum = (long long) N * (N + 1) / 2;
	for (int i = N; i > 0; i--) {
		if (sum - 2 * i >= 0) {
			sum -= 2 * i;
		}
	}
	
	cout << 15 + sum << endl;
	
	return 0;
}