// Problem: 256_B. Mr. Bender and Square
// Time complexity: logn
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.BufferedWriter;
import java.util.InputMismatchException;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.NoSuchElementException;
import java.io.Writer;
import java.math.BigInteger;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 * @author Egor Kulikov (egor@egork.net)
 */
public class Main {
	public static void main(String[] args) {
		InputStream inputStream = System.in;
		OutputStream outputStream = System.out;
		InputReader in = new InputReader(inputStream);
		OutputWriter out = new OutputWriter(outputStream);
		TaskB solver = new TaskB();
		solver.solve(1, in, out);
		out.close();
	}
}

class TaskB {
	public void solve(int testNumber, InputReader in, OutputWriter out) {
		int side = in.readInt();
		int row = in.readInt() - 1;
		int column = in.readInt() - 1;
		int required = in.readInt();
		long left = 0;
		long right = 2 * side - 2;
		while (left < right) {
			long current = (left + right) / 2;
			long result = calculate(row, column, current) + calculate(column, side - row - 1, current) +
				calculate(side - row - 1, side - column - 1, current) + calculate(side - column - 1, row, current) + 1;
			if (result >= required)
				right = current;
			else
				left = current + 1;
		}
		out.printLine(left);
	}

	private long calculate(int row, int column, long current) {
		column++;
		long total = 0;
		long mn = Math.min(row, column);
		long mx = Math.max(row, column);
		if (current <= mn)
			return current * (current + 1) / 2;
		total += mn * (mn + 1) / 2;
		current -= mn;
		mx -= mn;
		if (current <= mx)
			return total + mn * current;
		total += mn * mx;
		current -= mx;
		if (current < mn)
			return total + (mn - 1) * mn / 2 - (mn - current - 1) * (mn - current) / 2;
		return total + (mn - 1) * mn / 2;
	}
}

class InputReader {

	private InputStream stream;
	private byte[] buf = new byte[1024];
	private int curChar;
	private int numChars;
	private SpaceCharFilter filter;

	public InputReader(InputStream stream) {
		this.stream = stream;
	}

	public int read() {
		if (numChars == -1)
			throw new InputMismatchException();
		if (curChar >= numChars) {
			curChar = 0;
			try {
				numChars = stream.read(buf);
			} catch (IOException e) {
				throw new InputMismatchException();
			}
			if (numChars <= 0)
				return -1;
		}
		return buf[curChar++];
	}

	public int readInt() {
		int c = read();
		while (isSpaceChar(c))
			c = read();
		int sgn = 1;
		if (c == '-') {
			sgn = -1;
			c = read();
		}
		int res = 0;
		do {
			if (c < '0' || c > '9')
				throw new InputMismatchException();
			res *= 10;
			res += c - '0';
			c = read();
		} while (!isSpaceChar(c));
		return res * sgn;
	}

	public boolean isSpaceChar(int c) {
		if (filter != null)
			return filter.isSpaceChar(c);
		return isWhitespace(c);
	}

	public static boolean isWhitespace(int c) {
		return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
	}

	public interface SpaceCharFilter {
		public boolean isSpaceChar(int ch);
	}
}

class OutputWriter {
	private final PrintWriter writer;

	public OutputWriter(OutputStream outputStream) {
		writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
	}

	public OutputWriter(Writer writer) {
		this.writer = new PrintWriter(writer);
	}

	public void print(Object...objects) {
		for (int i = 0; i < objects.length; i++) {
			if (i != 0)
				writer.print(' ');
			writer.print(objects[i]);
		}
	}

    public void printLine(Object...objects) {
		print(objects);
		writer.println();
	}

	public void close() {
		writer.close();
	}

	}