import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.io.PrintWriter;
import java.util.ArrayList;

public class HR3 {

	static BufferedReader br;

	static PrintWriter pw = new PrintWriter(System.out);

	public static void main(String[] args) throws IOException {
		br = new BufferedReader(new InputStreamReader(System.in));

		solve();
		pw.close();
		br.close();

	}

	static void solve() throws IOException {
		
		int[]arr=readIntArr();
		int p=arr[0];
		int d=arr[1];
		int m=arr[2];
		int s=arr[3];
		
		int cnt=0;
		while(s>=p) {
			s-=p;
			cnt++;
			if(p>m) {
				p-=d;
				if(p<m)
					p=m;
			}
		}
		pw.print(cnt);
		
	}

	static public String readString() throws IOException {
		return br.readLine();

	}

	static public long readLong() throws IOException {
		return Long.parseLong(br.readLine());
	}

	static public int readInt() throws IOException {
		return Integer.parseInt(br.readLine());
	}

	static public int[] readIntArr() throws IOException {
		String[] str = br.readLine().split(" ");
		int arr[] = new int[str.length];
		for (int i = 0; i < arr.length; i++)
			arr[i] = Integer.parseInt(str[i]);
		return arr;
	}

	static public Integer[] readOIntArr() throws IOException {
		String[] str = br.readLine().split(" ");
		Integer arr[] = new Integer[str.length];
		for (int i = 0; i < arr.length; i++)
			arr[i] = new Integer(str[i]);
		return arr;
	}

	static public double[] readDoubleArr() throws IOException {
		String[] str = br.readLine().split(" ");
		double arr[] = new double[str.length];
		for (int i = 0; i < arr.length; i++)
			arr[i] = Double.parseDouble(str[i]);
		return arr;
	}

	static public Double[] readODoubleArr() throws IOException {
		String[] str = br.readLine().split(" ");
		Double arr[] = new Double[str.length];
		for (int i = 0; i < arr.length; i++)
			arr[i] = new Double(str[i]);
		return arr;
	}

	static public long[] readLongArr() throws IOException {
		String[] str = br.readLine().split(" ");
		long arr[] = new long[str.length];
		for (int i = 0; i < arr.length; i++)
			arr[i] = Long.parseLong(str[i]);
		return arr;
	}

	static public Long[] readOLongArr() throws IOException {
		String[] str = br.readLine().split(" ");
		Long arr[] = new Long[str.length];
		for (int i = 0; i < arr.length; i++)
			arr[i] = new Long(str[i]);
		return arr;
	}

	static public double readDouble() throws IOException {
		return Double.parseDouble(br.readLine());
	}
}