using System;
class Solution
{

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


        while (sum <= s)
        {
            sum = sum + p;
            if (p >= m)
            {
                p = p - d;
                if (p < m)
                {
                    p = m;
                }
            }
            else
            {
                p = m;
            }



            count++;
        }
        return count - 1;
    }

    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);
    }
}