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 count =0;
        int currentCost=p;
        int money=s;
        while (currentCost>=m){
            money=money-currentCost;
            currentCost=currentCost-d;
            count++;
            if (money<0){
                count--;
                currentCost=m-1;
            }
        }
        while (money>0){
            money =money -m;
            count++;
            if (money<0){
                count--;
            }
        }
        return count;
            
        
    }

    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();
    }
}