import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int m = sc.nextInt();
        int p = sc.nextInt();
        int q = sc.nextInt();
        int all = (12 + q) * m;
        int year = n / all;
        n %= all;
        for (int i = 1; i <= 12; i++) {
            n -= m;
            if (i >= p && i <= p + q - 1) {
                n -= m;
            }
            if (n <= 0) {
                System.out.println(year * 12 + i);
                return;
            }
        }
    }
}