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 total_price = 0;
        total_price = p;
        int previous_price = p;
        int cnt =0;
        while(total_price <= s){
            if(previous_price - d > m){
               previous_price = previous_price - d; 
            }
            else{
                previous_price = m;
            }
            total_price = total_price + previous_price;
            cnt++;
        }
        return cnt;
    }

    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();
    }
}