import java.util.*;

public class Solution {

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

    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();
    }
}