import java.util.Scanner;

public class Main {

	@SuppressWarnings("resource")
	public static void main(String args[]) {
		Scanner scanner = new Scanner(System.in);
		int n=scanner.nextInt();
		int m=scanner.nextInt();
		int p=scanner.nextInt();
		int q=scanner.nextInt();
		
		int mon=0;
		int ans=0;
		while(n>0) {
			mon++;
			if(mon==13) {
				mon=1;
			}
			if(p<=mon&&mon<p+q) {
				n-=2*m;
			}
			else {
				n-=m;
			}
			ans++;
		}
		System.out.println(ans);
	}
}