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 c = 0;
        while (true){
            s -= p;
            if (s < 0){
                break;
            }
            c ++;
            if (p > m){
                p -= d;
            }
            
            if (p < m){
                p = m;
            }
        }
        return c;
    }

    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);
    }
}