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 games=0; int cost=0;int current=p;
        while(current>m && cost<s){
            cost+=current;
            if(cost>s){
                break;
            }
            current-=d;
            games++;
        }
        while(cost<s){
            cost+=m;
                        if(cost>s){
                break;
            }
            games++;
        }
        return games;
    }

    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();
    }
}