using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
class Solution {

    static int howManyGames(int startPrice, int decrease, int min, int balance) {
        // Return the number of games you can buy
        int books =0;
        while (balance >0)
        {
            balance -= startPrice;
            startPrice -= decrease;
            if (startPrice <= min)
            {startPrice=min;
            decrease=0;}
            if (balance >=0){
            books++;}
        }
        return books;
    }

    static void Main(String[] args) {
        string[] tokens_p = Console.ReadLine().Split(' ');
        int p = Convert.ToInt32(tokens_p[0]);
        int d = Convert.ToInt32(tokens_p[1]);
        int m = Convert.ToInt32(tokens_p[2]);
        int s = Convert.ToInt32(tokens_p[3]);
        int answer = howManyGames(p, d, m, s);
        Console.WriteLine(answer);
    }
}