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 count = 0;
        
        while(s >= p) {
            count++;
            s = s - p;
            p = AdjustPrice(p-d, m);
        }
        
        return count;
    }
    
    static int AdjustPrice(int s, int m){
        if(s >= m) return s;
        return m;
    }

    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);
    }
}