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
        
        if(s < p)
        {
            return 0;
        }
        int cost = p;
        int items = 0;
        while(s > 0 &&  cost > m)
        {
//System.out.println("cost: "+cost);
            items++;
            s = s-cost;
            cost = cost-d;
        }
        items = items + s/m;
        
        return items;
    }

    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();
    }
}