import java.io.*;

public class MCompet {
	private static int inBufNextByte, inBufNextIndex, inBufCurReadByteSize;
	private static int outBufNextIndex;
	private static InputStream is = System.in;
	private static OutputStream os = System.out;
	private static final int IN_BUF_SIZE = (1 << 15);
	private static final int OUT_BUF_SIZE = (1 << 15);
	private static final byte IN_BUFFER[] = new byte[IN_BUF_SIZE];
	private static final byte OUT_BUFFER[] = new byte[OUT_BUF_SIZE];
	private static final String IN_FILE_PATH = new File("").getAbsolutePath() + "/in.txt";
	private static final String OUT_FILE_PATH = new File("").getAbsolutePath() + "/out.txt";
	private static final String LINE_SEPARATOR = System.getProperty("line.separator");

	private MCompet() throws Exception {
		if (INPUT_FROM_FILE) is = new FileInputStream(IN_FILE_PATH);
		if (OUTPUT_TO_FILE) os = new FileOutputStream(OUT_FILE_PATH);
		nc();
		solve();
		is.close();
		flushOutBuf();
		os.close();
	}

	public static void main(String[] args) {
		try {
			new MCompet();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	private boolean isDigit(int cp) {
		return 48 <= cp && cp <= 57;
	}

	private boolean isLowercase(int cp) {
		return 97 <= cp && cp <= 122;
	}

	private boolean isUppercase(int cp) {
		return 65 <= cp && cp <= 90;
	}

	private boolean isAlphabet(int cp) {
		return isLowercase(cp) || isUppercase(cp);
	}

	private boolean isCharacter(int cp) {
		return cp != -1;
	}

	private boolean isWhitespace(int cp) {
		return (9 <= cp && cp <= 13) || (cp == 32);
	}

	private boolean isWordSeparator(int cp) {
		return (9 <= cp && cp <= 13) || (cp == 32) || (cp == '@') || (cp == ';');
	}

	private boolean isLineSeparator(int cp) {
		return cp == 10 || cp == 13;
	}

	private int nc() throws IOException {
		if (inBufNextIndex >= inBufCurReadByteSize) {
			inBufCurReadByteSize = is.read(IN_BUFFER, 0, IN_BUF_SIZE);
			if (inBufCurReadByteSize == -1) return inBufNextByte = -1;
			inBufNextIndex = 0;
		}
		return inBufNextByte = IN_BUFFER[inBufNextIndex++];
	}

	private char[] nc(int n) throws IOException {
		while (isWhitespace(inBufNextByte)) nc();
		char a[] = new char[n];
		for (int i = 0; i < n; ++i) {
			a[i] = (char) inBufNextByte;
			nc();
		}
		return a;
	}

	private char[][] nc(int r, int c) throws IOException {
		char a[][] = new char[r][c];
		for (int i = 0; i < r; ++i) a[i] = nc(c);
		return a;
	}

	private boolean isMinus() throws IOException {
		boolean minus = false;
		while (inBufNextByte == '+' || inBufNextByte == '-') {
			if (inBufNextByte == '-') minus = !minus;
			nc();
		}
		return minus;
	}

	private Integer ni() throws IOException {
		while (isWhitespace(inBufNextByte)) nc();
		int res = 0;
		boolean minus = isMinus();
		if (!isDigit(inBufNextByte)) return null;
		while (true) {
			res = (res << 1) + (res << 3) + inBufNextByte - '0';
			if (!isDigit(nc())) break;
		}
		return minus ? -res : res;
	}

	private int[] ni(int n) throws IOException {
		int a[] = new int[n];
		for (int i = 0; i < n; ++i) a[i] = ni();
		return a;
	}

	private int[][] ni(int r, int c) throws IOException {
		int a[][] = new int[r][c];
		for (int i = 0; i < r; ++i) a[i] = ni(c);
		return a;
	}

	private Long nl() throws IOException {
		while (isWhitespace(inBufNextByte)) nc();
		long res = 0;
		boolean minus = isMinus();
		if (!isDigit(inBufNextByte)) return null;
		while (true) {
			res = (res << 1) + (res << 3) + inBufNextByte - '0';
			if (!isDigit(nc())) break;
		}
		return minus ? -res : res;
	}

	private long[] nl(int n) throws IOException {
		long a[] = new long[n];
		for (int i = 0; i < n; ++i) a[i] = nl();
		return a;
	}

	private long[][] nl(int r, int c) throws IOException {
		long a[][] = new long[r][c];
		for (int i = 0; i < r; ++i) a[i] = nl(c);
		return a;
	}

	private Double nd() throws IOException {
		while (isWhitespace(inBufNextByte)) nc();
		boolean minus = isMinus();
		if (!isDigit(inBufNextByte)) return null;
		StringBuilder sb = new StringBuilder();
		sb.append((char) inBufNextByte);
		while (isDigit(nc())) sb.append((char) inBufNextByte);
		if (inBufNextByte == '.') {
			sb.append('.');
			while (isDigit(nc())) sb.append((char) inBufNextByte);
		}
		double res = Double.parseDouble(sb.toString());
		return minus ? -res : res;
	}

	private double[] nd(int n) throws IOException {
		double a[] = new double[n];
		for (int i = 0; i < n; ++i) a[i] = nd();
		return a;
	}

	private double[][] nd(int r, int c) throws IOException {
		double a[][] = new double[r][c];
		for (int i = 0; i < r; ++i) a[i] = nd(c);
		return a;
	}

	private String line() throws IOException {
		while (isWhitespace(inBufNextByte)) nc();
		StringBuilder sb = new StringBuilder();
		while (isCharacter(inBufNextByte) && !isLineSeparator(inBufNextByte)) {
			sb.append((char) inBufNextByte);
			nc();
		}
		return sb.toString();
	}

	private String ns() throws IOException {
		while (isWordSeparator(inBufNextByte)) nc();
		StringBuilder sb = new StringBuilder();
		while (isCharacter(inBufNextByte) && !isWordSeparator(inBufNextByte)) {
			sb.append((char) inBufNextByte);
			nc();
		}
		return sb.toString();
	}

	private String[] ns(int n) throws IOException {
		String a[] = new String[n];
		for (int i = 0; i < n; ++i) a[i] = ns();
		return a;
	}

	private String[][] ns(int r, int c) throws IOException {
		String a[][] = new String[r][c];
		for (int i = 0; i < r; ++i) a[i] = ns(c);
		return a;
	}

	private void flushOutBuf() {
		if (outBufNextIndex == 0) return;
		try {
			os.write(OUT_BUFFER, 0, outBufNextIndex);
			os.flush();
			outBufNextIndex = 0;
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	private void print(String format, Object[] args) {
		if (args != null) format = String.format(format, args);
		for (int i = 0, n = format.length(); i < n; ++i) {
			OUT_BUFFER[outBufNextIndex++] = (byte) format.charAt(i);
			if (outBufNextIndex >= OUT_BUF_SIZE) flushOutBuf();
		}
	}

	private <T> void print(T ob) {
		print(ob + "", null);
	}

	private <T> void println(T ob) {
		print(ob + LINE_SEPARATOR, null);
	}

	private void println(String format, Object... args) {
		print(format + LINE_SEPARATOR, args);
	}

	private <T> void log(T ob) {
		print("\u001B[31m" + ob + "\u001B[0m", null);
	}

	private <T> void log(String format, Object... args) {
		print("\u001B[31m" + format + "\u001B[0m", args);
	}

	private <T> void logln(T ob) {
		print("\u001B[31m" + ob + "\u001B[0m\n", null);
	}

	private void logln(String format, Object... args) {
		print("\u001B[31m" + format + "\u001B[0m\n", args);
	}

	int mod = (int) 1E9 + 7;

	private void solve() throws Exception {
		int cost = ni(), diff = ni(), min = ni(), s = ni();
		int ans = 0, sum = 0;
		while (true) {
			sum += cost;
			if (sum > s) break;
			++ans;
			if (cost - diff > min) cost -= diff;
			else cost = min;
		}
		println(ans);
	}

	private static final boolean INPUT_FROM_FILE = false, OUTPUT_TO_FILE = false;
}