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 amount = 0;
    if (p > s) {
      return 0;
    }

    while (s - p >= 0) {
      amount++;
      s -= p;
      if (p > m) {
        p -= d;
        if (p < m) {
          p = m;
        }
      }
    }
    
    return amount;
  }

  public static void main(String[] args) {
    try (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);
    }
  }
}