import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int N = scan.nextInt();
		int M = scan.nextInt();
		int P = scan.nextInt();
		int Q = scan.nextInt();
		scan.close();
		int t = 0;
		int cnt = 0;
		while(N > 0) {
			if(t >= P - 1 && t < P + Q - 1) {
				N -= 2 * M;
			}else {
				N -= M;
			}
			t ++;
			t = t % 12;
			cnt ++;
		}
		System.out.println(cnt);
	}
}