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 gamesBought = 0;
        int currentGamePrice = p;
        
        
        while (currentGamePrice <= s){
            s -= currentGamePrice;
            if(currentGamePrice > m){
            currentGamePrice -= d;
                if(currentGamePrice < m){
                    currentGamePrice = m;
                }
            }
            gamesBought++;
        }
        return gamesBought;
    }

    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();
    }
}