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

    static int howManyGames(int p, int d, int m, int s)
    {
        int count = 0;

        int rem = s;

        int currentCost = p;

        while(rem>0)
        {
            if (rem >= currentCost)
            {
                count++;
                rem = rem - currentCost;
                currentCost = currentCost - d;
                if (currentCost < m)
                    currentCost = m;
            }
            else
                break;

        }
        return count;

    }

    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);
    }
}