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) {
        int price = p;
        int item = 0;
        int sumBought = 0;
        while(price >= m && sumBought<=s){
          item++;
          sumBought += price;
          price -=d;
        }
        if(sumBought > s) {
          item--;
        }
        if(sumBought<s){
          item += (s-sumBought)/m;
        }
      
        return item;
    }

    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();
    }
}