Two best friends Serozha and Gena play a game.

Initially there is one pile consisting of n stones on the table. During one move one pile should be taken and divided into an arbitrary number of piles consisting of a1 > a2 > ... > ak > 0 stones. The piles should meet the condition a1 - a2 = a2 - a3 = ... = ak - 1 - ak = 1. Naturally, the number of piles k should be no less than two.

The friends play in turns. The player who cannot make a move loses. Serozha makes the first move. Who will win if both players play in the optimal way?

Input

The single line contains a single integer n (1 ≤ n ≤ 105).

Output

If Serozha wins, print k, which represents the minimal number of piles into which he can split the initial one during the first move in order to win the game.

If Gena wins, print "-1" (without the quotes).

Examples

Input

3


Output

2


Input

6


Output

-1


Input

100


Output

8
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.DataInputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.math.MathContext;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.BitSet;
import java.util.Collections;
import java.util.Comparator;
import java.util.Deque;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Hashtable;
import java.util.InputMismatchException;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.Random;
import java.util.Set;
import java.util.Stack;
import java.util.StringTokenizer;
import java.util.TreeMap;
import java.util.TreeSet;

import static java.lang.Double.*;
import static java.math.BigInteger.*;
import static java.lang.Math.*;
import static java.util.Arrays.*;
import static java.util.Collections.*;

public class Main implements Runnable {

	// private long start;

	private void solve() throws IOException {
		// start = System.currentTimeMillis();
		init();
		readData();
		processing();
	}
	
	private void init() {
	}
	
	HashSet<Integer> si = new HashSet<Integer>();
	
	private int mex(List<Integer> lst) {
		si.clear();
		si.addAll(lst);
		int ret = 0;
		while (si.contains(ret)) {
			++ret;
		}
		return ret;
	}
	
	private void processing() {
		nim = new int[100001];
		nim[0] = 0;
		nim[1] = 0;
		nim[2] = 0;
		nim[3] = 1;
		List<Integer> fg = new ArrayList<Integer>();
		int[] firstTurn = new int[100001];
		firstTurn[3] = 2;
		for (int i = 4; i < 100001; ++i) {
			fg.clear();
			int memo = -1;
			for (int j = 2; j*j <= 2*i; ++j) {
				if (2*i%j == 0) {
					int n = 2*i/j - 1 + j;
					if (n%2 == 0) {
						n /= 2;
						if (n - j + 1 > 0) {
							int xor = 0;
							for (int l = n; l >= n - j + 1; --l) {
								xor ^= nim[l];
							}
							if (xor == 0 && memo == -1) {
								memo = j;
							}
							fg.add(xor);
						}
					}					
				}
			}
			nim[i] = mex(fg);
			firstTurn[i] = memo;
		}
		if (nim[nn] == 0) {
			println(-1);
		}
		else {
			println(firstTurn[nn]);
		}
	}

	private void readData() throws IOException {
		nn = nextInt();
	}

	private int nn;
	
	private int[] nim;
	
	public static void main(String[] args) throws InterruptedException {
		new Thread(null, new Runnable() {
			public void run() {
				new Main().run();
			}
		}, "1", 1 << 24).start();
	}

	// @Override
	public void run() {
		try {
			boolean onlineJudge = System.getProperty("ONLINE_JUDGE") != null;
			reader = onlineJudge ? new BufferedReader(new InputStreamReader(
					System.in)) : new BufferedReader(
					new FileReader("input.txt"));
			writer = onlineJudge ? new PrintWriter(new BufferedWriter(
					new OutputStreamWriter(System.out))) : new PrintWriter(
					new BufferedWriter(new FileWriter("output.txt")));
			Locale.setDefault(Locale.US);
			tokenizer = null;
			solve();
			writer.flush();
		} catch (Exception error) {
			error.printStackTrace();
			System.exit(1);
		}
	}

	class InputReader {

		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 long readLong() {
			int c = read();
			while (isSpaceChar(c))
				c = read();
			int sgn = 1;
			if (c == '-') {
				sgn = -1;
				c = read();
			}
			long 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 String readString() {
			int c = read();
			while (isSpaceChar(c))
				c = read();
			StringBuffer res = new StringBuffer();
			do {
				res.appendCodePoint(c);
				c = read();
			} while (!isSpaceChar(c));
			return res.toString();
		}

		private boolean isSpaceChar(int c) {
			return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
		}

		private String readLine0() {
			StringBuffer buf = new StringBuffer();
			int c = read();
			while (c != '\n' && c != -1) {
				if (c != '\r')
					buf.appendCodePoint(c);
				c = read();
			}
			return buf.toString();
		}

		public String readLine() {
			String s = readLine0();
			while (s.trim().length() == 0)
				s = readLine0();
			return s;
		}

		public String readLine(boolean ignoreEmptyLines) {
			if (ignoreEmptyLines)
				return readLine();
			else
				return readLine0();
		}

		public char readCharacter() {
			int c = read();
			while (isSpaceChar(c))
				c = read();
			return (char) c;
		}

		public double readDouble() {
			int c = read();
			while (isSpaceChar(c))
				c = read();
			int sgn = 1;
			if (c == '-') {
				sgn = -1;
				c = read();
			}
			double res = 0;
			while (!isSpaceChar(c) && c != '.') {
				if (c == 'e' || c == 'E')
					return res * Math.pow(10, readInt());
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res *= 10;
				res += c - '0';
				c = read();
			}
			if (c == '.') {
				c = read();
				double m = 1;
				while (!isSpaceChar(c)) {
					if (c == 'e' || c == 'E')
						return res * Math.pow(10, readInt());
					if (c < '0' || c > '9')
						throw new InputMismatchException();
					m /= 10;
					res += (c - '0') * m;
					c = read();
				}
			}
			return res * sgn;
		}

		private InputStream stream;
		private byte[] buf = new byte[1 << 16];
		private int curChar;
		private int numChars;
	}

	private class Parser {

		public Parser(InputStream in) {
			din = new DataInputStream(in);
			buffer = new byte[BUFFER_SIZE];
			bufferPointer = bytesRead = 0;
		}

		public byte c;

		public int nextInt() throws IOException {
			int value = 0;
			c = read();
			while (c <= ' ')
				c = read();
			boolean neg = c == '-';
			if (neg)
				c = read();
			do {
				value = value * 10 + c - 48;
				c = read();
			} while (c > ' ');
			if (neg) {
				return -value;
			} else {
				return value;
			}
		}

		private void fillBuffer() throws IOException {
			bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE);
			if (bytesRead == -1)
				buffer[0] = -1;
		}

		public byte read() throws IOException {
			if (bufferPointer == bytesRead)
				fillBuffer();
			return buffer[bufferPointer++];
		}

		private DataInputStream din;
		private byte[] buffer;
		private int bufferPointer, bytesRead;

		final private int BUFFER_SIZE = 1 << 16;
	}

	private BufferedReader reader;
	private PrintWriter writer;
	private StringTokenizer tokenizer;

	private void println() {
		writer.println();
	}

	private void print(Object obj) {
		writer.print(obj);
	}

	private void println(Object obj) {
		writer.println(obj);
	}

	private void printf(String f, Object... obj) {
		writer.printf(f, obj);
	}

	private int nextInt() throws IOException {
		return Integer.parseInt(nextToken());
	}

	private long nextLong() throws IOException {
		return Long.parseLong(nextToken());
	}

	private double nextDouble() throws IOException {
		return Double.parseDouble(nextToken());
	}

	private String nextToken() throws IOException {
		while (tokenizer == null || !tokenizer.hasMoreTokens()) {
			tokenizer = new StringTokenizer(reader.readLine());
		}
		return tokenizer.nextToken();
	}
}