#include <iostream>
using namespace std;

int n, m, p, q;

int main() {
	int i;
	
	cin >> n >> m >> p >> q;
	for (i = 0; n > 0; i++) {
		if (p - 1 <= i % 12 && i % 12 <= p + q - 1) n -= 2 * m;
		else n -= m;
	}
	cout << i << endl;
	return 0;
}