import java.util.Scanner;

public class A {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int p = in.nextInt();
        int d = in.nextInt();
        int m = in.nextInt();
        int s = in.nextInt();
        int res = 0;
        while (s > 0) {
            if (s >= p) {
                ++res;
                s -= p;
            } else {
                break;
            }
            p -= d;
            if (p <= m) {
                p = m;
            }
        }
        System.out.println(res);
    }
}