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 count = 0;
        long total = 0;
        int last = 0;
        while(total<=s) {
            count++;
            if(count==1){
                total+=p;
                last = p;
            }else if(last-d>=m){
                last = last-d;
                total += last;
            }else{
                last = m;
                total +=last;
            }
            
        }
        return count-1;
    }

    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();
    }
}