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

    

    static void Main(String[] args) {
        var arr = Array.ConvertAll(Console.ReadLine().Split(), int.Parse);
            var price = arr[0];
            var discount = arr[1];
            var minimum = arr[2];
            var balance = arr[3];
            var count = 0;

            var currentPrice = price;
            while (balance >= currentPrice) {
                balance -= currentPrice;
                count++;
                currentPrice = Math.Max(currentPrice - discount, minimum);
            }
            Console.WriteLine(count);
    }
}