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

public class Solution {

    static int howManyGames(int startPrice, int saving, int minPrice, int budget) {
        // Return the number of games you can buy
        int count=0;
        int price = startPrice;
        while (true) {
            // check if budget is sufficient
            if (budget<price) {
                break;
            }
            
            // buy a game
            budget -= price;
            count++;
            
            // check if price needs adjustment
            price -= saving;
            if (price < minPrice) {
               price=minPrice;
            }
        }
        return count;
    }

    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 answer = howManyGames(p, d, m, s);
        System.out.println(answer);
        in.close();
    }
}