#include <bits/stdc++.h>
using namespace std;

void dg(int a, int c, int p) {
	if (a == c) {
		p++;
		return;
	}
	dg(a, c++, p);
	if (c >= 2) {
		dg(a, c + 2, p);
	}
	return;
}

int main() {
	int a, b = 0, p = 0;
	cin >> a;
	dg(a, b, p);
	cout << p;
}