Keju Mozarella Khas Malang

import java.io.*;
import java.util.*;

public class Solution {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int p = sc.nextInt(), d = sc.nextInt(), m = sc.nextInt(), v = sc.nextInt(), total = 0;
        for(int i = 0; v >= 0; i++) {
            if (i == 0) v -= p;
            else v -= Math.max(p - d * i, m);
            total++;
        }
        System.out.println(--total);
    }
}