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)
        {
            var gameCount = 0;
            var cost = p;

            while(s >= cost)
            {
                gameCount += 1;
                s -= cost;

                cost -= d;

                if(cost < m)
                {
                    cost = m;
                }
            }

            return gameCount;
        }

    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);
    }
}