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

    // p - starting price
    // d - discount on the next game
    // m - min price
    // s - how much money you have
    static int howManyGames(int p, int d, int m, int s) {
        // Return the number of games you can buy
        bool canBuyGames = true;
        int numOfGames = 0;
        while (canBuyGames)
        {
            if ((s-p) >= 0)
            {
                numOfGames++;
                s -= p;
                
                if((p-d > m))
                {
                    p -= d;
                }
                else
                {
                    p = m;
                }
            }
            else
            {
                canBuyGames = false;
            }
        }
        
        return numOfGames;
        
    }

    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);
    }
}