Problem: A maze is composed of a grid of H \times W squares - H vertical, W horizontal.

The square at the i-th row from the top and the j-th column from the left - (i,j) - is a wall if S_{ij} is `#` and a road if S_{ij} is `.`.

There is a magician in (C_h,C_w). He can do the following two kinds of moves:

* Move A: Walk to a road square that is vertically or horizontally adjacent to the square he is currently in.
* Move B: Use magic to warp himself to a road square in the 5\times 5 area centered at the square he is currently in.



In either case, he cannot go out of the maze.

At least how many times does he need to use the magic to reach (D_h, D_w)?

Constraints

* 1 \leq H,W \leq 10^3
* 1 \leq C_h,D_h \leq H
* 1 \leq C_w,D_w \leq W
* S_{ij} is `#` or `.`.
* S_{C_h C_w} and S_{D_h D_w} are `.`.
* (C_h,C_w) \neq (D_h,D_w)

Input

Input is given from Standard Input in the following format:


H W
C_h C_w
D_h D_w
S_{11}\ldots S_{1W}
\vdots
S_{H1}\ldots S_{HW}


Output

Print the minimum number of times the magician needs to use the magic. If he cannot reach (D_h,D_w), print `-1` instead.

Examples

Input

4 4
1 1
4 4
..#.
..#.
.#..
.#..


Output

1


Input

4 4
1 4
4 1
.##.


.##.


Output

-1


Input

4 4
2 2
3 3
....
....
....
....


Output

0


Input

4 5
1 2
2 5
.###
.
..##
..##


Output

2

Solution (in JAVA):

Solution:

import java.io.*;
import java.util.*;

import java.math.*;

 class Main {

	// static long sx = 0, sy = 0, mod = (long) (998244353);

	static ArrayList<Integer>[] a;
	static ArrayList<Long> p;
	static Integer[][] dp;
	static HashMap<ArrayList<Integer>, Long> hm = new HashMap<>();
	static boolean[][] vis;
	static int[] farr;
	static long[] far;
	public static PrintWriter out = new PrintWriter(System.out);
	static ArrayList<pair> pa = new ArrayList<>();
	static long[] fact = new long[(int) 1e6];
	static StringBuilder sb = new StringBuilder();
	static boolean cycle = false;
	static long mo = (long) (1e9 + 7);
	static int[] c, col;
	// static int n = 0, m, x, k;
	static int ans = Integer.MAX_VALUE;
	static boolean b = true;
	static boolean[] reach = new boolean[6000];
	static int[][] par;
	static int[] depth;
	static int[] size;
	static long[] pow;
	static int time = 0;
	static int[] disc;
	static int[] low;
	static char[][] ch;
	// static int cnt = 0;
	static int[][] dirs = { { -1, 0 }, { 0, 1 }, { 1, 0 }, { 0, -1 }, };
	static int n = 0, k = 0, z = 0;
	static long[] val;
	static String s1, s2;
	static long x, y;
	static int m = 0;

	public static void main(String[] args) throws IOException {

		Scanner scn = new Scanner(new BufferedReader(new InputStreamReader(System.in)));

		int n = scn.nextInt(), m = scn.nextInt();

		int sr = scn.nextInt() - 1, sc = scn.nextInt() - 1, dr = scn.nextInt() - 1, dc = scn.nextInt() - 1;

		char[][] ch = new char[n][m];

		for (int i = 0; i < n; i++) {

			String s = scn.next();

			for (int j = 0; j < m; j++)
				ch[i][j] = s.charAt(j);
		}

		if (ch[sr][sc] == '#' || ch[dr][dc] == '#') {
			System.out.println(-1);
			return;
		}

		boolean[][] vis = new boolean[n][m];
		PriorityQueue<pair> pq = new PriorityQueue<>();

		pq.add(new pair(sr, sc, 0));

		while (pq.size() != 0) {

			pair rp = pq.remove();

			if (vis[rp.i][rp.j])
				continue;

			if (rp.i == dr && rp.j == dc) {
				System.out.println(rp.cnt);
				return;
			}
			vis[rp.i][rp.j] = true;

			for (int i = Math.max(0, rp.i - 2); i <= Math.min(rp.i + 2, n - 1); i++) {

				for (int j = Math.max(0, rp.j - 2); j <= Math.min(rp.j + 2, m - 1); j++) {

					if (!vis[i][j] && ch[i][j] == '.') {

						pq.add(new pair(i, j, rp.cnt + (Math.abs(rp.i - i) + Math.abs(rp.j - j) == 1 ? 0 : 1)));

					}
				}
			}
		}

		System.out.println(-1);
	}

	// _________________________TEMPLATE_____________________________________________________________

	// public static long lcm(long x, long y) {
	//
	// return (x * y) / gcd(x, y);
	// }
	//
	// private static long gcd(long x, long y) {
	// if (x == 0)
	// return y;
	//
	// return gcd(y % x, x);
	// }

	//
	// static class comp implements Comparator<Integer> {
	//
	// @Override
	// public int compare(Integer p1, Integer p2) {
	//
	// return p2 - p1;
	//
	// }
	// }
	//
	// }
	//
	// public static long pow(long a, long b, long mod) {
	//
	// if (b < 0)
	// return 0;
	// if (b == 0 || b == 1)
	// return (long) Math.pow(a, b);
	//
	// if (b % 2 == 0) {
	//
	// long ret = pow(a, b / 2, mod);
	// ret = (ret % mod * ret % mod) % mod;
	// return ret;
	// }
	//
	// else {
	// return ((pow(a, b - 1, mod) % mod) * a % mod) % mod;
	// }
	// }

	private static class pair implements Comparable<pair> {

		int i;
		int j;
		int cnt;

		pair(int a, int b, int c) {
			i = a;
			j = b;
			cnt = c;
		}

		@Override
		public int compareTo(pair o) {

			return this.cnt - o.cnt;
		}

		// @Override
		//
		// public int hashCode() {
		// return i;
		// }
		//
		// @Override
		//
		// public boolean equals(Object o) {
		//
		// pair p = (pair) o;
		// return this.i == p.i;
		// }

	}

	private static class pair1 {

		int a, b;

		pair1(int a, int b) {
			this.a = a;
			this.b = b;
		}

	}

	private static String reverse(String s) {

		return new StringBuilder(s).reverse().toString();
	}

	public static class Reader {
		final private int BUFFER_SIZE = 1 << 16;
		private DataInputStream din;
		private byte[] buffer;
		private int bufferPointer, bytesRead;

		public Reader() {
			din = new DataInputStream(System.in);
			buffer = new byte[BUFFER_SIZE];
			bufferPointer = bytesRead = 0;
		}

		public Reader(String file_name) throws IOException {
			din = new DataInputStream(new FileInputStream(file_name));
			buffer = new byte[BUFFER_SIZE];
			bufferPointer = bytesRead = 0;
		}

		public String readLine() throws IOException {
			byte[] buf = new byte[1000000 + 1]; // line length
			int cnt = 0, c;
			while ((c = read()) != -1) {
				if (c == '\n')
					break;
				buf[cnt++] = (byte) c;
			}
			return new String(buf, 0, cnt);
		}

		public int nextInt() throws IOException {
			int ret = 0;
			byte c = read();
			while (c <= ' ')
				c = read();
			boolean neg = (c == '-');
			if (neg)
				c = read();
			do {
				ret = ret * 10 + c - '0';
			} while ((c = read()) >= '0' && c <= '9');

			if (neg)
				return -ret;
			return ret;
		}

		public long nextLong() throws IOException {
			long ret = 0;
			byte c = read();
			while (c <= ' ')
				c = read();
			boolean neg = (c == '-');
			if (neg)
				c = read();
			do {
				ret = ret * 10 + c - '0';
			} while ((c = read()) >= '0' && c <= '9');
			if (neg)
				return -ret;
			return ret;
		}

		public double nextDouble() throws IOException {
			double ret = 0, div = 1;
			byte c = read();
			while (c <= ' ')
				c = read();
			boolean neg = (c == '-');
			if (neg)
				c = read();

			do {
				ret = ret * 10 + c - '0';
			} while ((c = read()) >= '0' && c <= '9');

			if (c == '.') {
				while ((c = read()) >= '0' && c <= '9') {
					ret += (c - '0') / (div *= 10);
				}
			}

			if (neg)
				return -ret;
			return ret;
		}

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

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

		public void close() throws IOException {
			if (din == null)
				return;
			din.close();
		}

		public int[] nextIntArray(int n) throws IOException {
			int[] arr = new int[n];
			for (int i = 0; i < n; i++) {
				arr[i] = nextInt();
			}
			return arr;
		}

		public long[] nextLongArray(int n) throws IOException {
			long[] arr = new long[n];
			for (int i = 0; i < n; i++) {
				arr[i] = nextLong();
			}
			return arr;
		}

		public int[][] nextInt2DArray(int m, int n) throws IOException {
			int[][] arr = new int[m][n];
			for (int i = 0; i < m; i++) {
				for (int j = 0; j < n; j++)
					arr[i][j] = nextInt();
			}
			return arr;
		}

		public long[][] nextInt2DArrayL(int m, int n) throws IOException {
			long[][] arr = new long[m][n];
			for (int i = 0; i < m; i++) {
				for (int j = 0; j < n; j++)
					arr[i][j] = nextInt();
			}
			return arr;
		}
		// kickstart - Solution
		// atcoder - Main
	}

}