56
 1
 46
 63478
 7578
 56056
 78
 66873
 8149
 35708
 81207
 41385
 37317
 74424
 67817
 684
 15
 96992
 38798
 19715
 627
 39509
 45899
 31893
 1515
 33
 95298
 27443
 60879
 99
 34378
 57113
 36655
 63359
 873
 67341
 100000
 42863
 35
 250
 573
 23
 871
 15748
 92763
 9564
 42602
 38
 42237
 70878
 93764
 303

-1
 -1
 4
 -1
 3
 -1
 4
 2
 2
 -1
 6
 15
 -1
 21
 73
 -1
 2
 -1
 76
 -1
 2
 -1
 -1
 3
 2
 2
 4
 2
 2
 2
 -1
 2
 -1
 34
 18
 2
 -1
 -1
 -1
 5
 3
 -1
 -1
 8
 22
 3
 17
 -1
 18
 -1
 -1
 2

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] = nim[1] = nim[2] = 0;
		List<Integer> fg = new ArrayList<Integer>();
		Map<Integer, Integer> firstTurn = new Hashtable<Integer, Integer>();
		for (int i = 3; 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;
								firstTurn.put(i, memo);
							}
							fg.add(xor);
						}
					}					
				}
			}
			nim[i] = mex(fg);
		}
		if (nim[nn] == 0) {
			println(-1);
		}
		else {
			println(firstTurn.get(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();
	}
}