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

public class Solution {

    // Implementation: Semiprimes
    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 cnt = 0;

        while (s > 0)
        {
            cnt++;
            s -= p;
            p -= d;
            if (p <= m)
            {
                p = m;
                d = 0;
            }
        }
        if (s < 0)
            cnt--;
        System.out.println(cnt);
    }
}