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) {
        // Return the number of games you can buy
        int count = 0;
            int cost = p;
            while (s > 0 && s>= cost) {
                count++;
                s -= cost;
                if (cost - d > m) {
                    cost -= d;
                }
                else cost = m;
            }
            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);
    }
}