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 nextPrice = p;
        int result = 0;
        while(true) {
            if (s<nextPrice) {
                break;
            }
            result++;
            s-=nextPrice;
            nextPrice = nextPrice - d;
            if (nextPrice < m) {
                nextPrice = 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();
    }
}