import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        int initialPrice = scanner.nextInt();
        int moneyToSubtract = scanner.nextInt();
        int threshold = scanner.nextInt();
        int dollarsAvailable = scanner.nextInt();
        int currentPrice = initialPrice;

        int totalGamesBought = 0;

        while (dollarsAvailable > 0) {
            int moneyToPay = Math.max(currentPrice, threshold);

            if(dollarsAvailable - moneyToPay >= 0) {
                totalGamesBought++;
            }

            dollarsAvailable -= moneyToPay;

            currentPrice -= moneyToSubtract;
        }

        System.out.println(totalGamesBought);
    }
}