import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    static int howManyGames(int p, int d, int m, int s) {
        // Return the number of games you can buy
        int tot = s;
        int f = 0;
        int turn = 0;
        int cost = p;
        while(tot >= m)
        {
            if(turn == 0)
            {
                tot -= p;
                cost = p - d;
                if(tot < 0)
                    break;
            }
            else if(cost > m)
            {
                tot -= cost;
                cost -= d;
                if(cost < m)
                    cost = m;
                if(tot < 0)
                    break;
            }
            else
            {
                tot -= m;
                if(tot < 0)
                    break;
            }
            turn++;
        }
        return turn;
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int p = in.nextInt();
        int d = in.nextInt();
        int m = in.nextInt();
        int s = in.nextInt();
        int answer = howManyGames(p, d, m, s);
        System.out.println(answer);
        in.close();
    }
}