import java.util.*;

public class CODE {

    static Scanner sc = new Scanner(System.in);

    static void solve() {

    }

    public static void main(String[] args) {
        int p = sc.nextInt(); // unit price
        int d = sc.nextInt(); // 56m
        int m = sc.nextInt(); // last step
        int s = sc.nextInt(); // my money

        int c = 0;

        while (s > 0) {
            c++;
            s -= p;
            if (p - d > m) {
                p -= d;
            } else {
                p = m;
            }
        }

        if (s < 0) {
            c--;
        }

        System.out.println(c);
    }

}