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

public class Solution {

    static int howManyGames(int p, int d, int m, int s) {
        // Return the number of games you can buy
        
        int num = 0, price = p;
        
        //if(price <= m){
        //    price = m;
        //}
        while(s-price >= 0){
            s -= price;
            num++;
            
            price -= d;
            
            if(price <= m){
                price = m;
            }
        }
        return num;
    }

    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();
    }
}