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) {
        int price = p;
        int result = 0;
        while(s > 0) {
            s -= p;
            if (s >= 0) {
                result++;
                if (p > m) {
                    p -= d;
                    if (p < m) p = m;
                }
            }
        }
        return result;
    }

    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();
    }
}