#include <fstream>
#include <iostream>


int main() {

	//std::ifstream inf("Text.txt");	std::cin.rdbuf(inf.rdbuf());

	int N = 0, M = 0, P = 0, Q = 0;
	std::cin >> N >> M >> P >> Q;

	int ans = 0;
	int now = -1;
	bool month[12] = { false };

	for (int i = 0; i < Q; i++) {
		month[P + i - 1] = true;
	}
	

	while (N > 0) {
		ans = ans + 1;
		now = (now + 1) % 12;

		if (month[now]) {
			N = N - M * 2;
		}
		else {
			N = N - M;
		}
	}

	std::cout << ans << std::endl;

	return 0;

}