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) {
        boolean canBuy = true;
        int bought = 0;
        if(s<p){
            return 0;
        }
        while ( canBuy){
            if (s>=p){
                s-=p;
                p-=d;
                if(p<m){
                    p=m;
                }
            }
            bought++;
            canBuy = false;
            if(s>=p){
                canBuy =true;
            }
        }
        return bought;
        // Return the number of games you can buy
    }

    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();
    }
}