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.DataInputStream; 
import java.io.FileInputStream; 
import java.io.IOException; 
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.Scanner; 
import java.util.StringTokenizer; 
import java.io.BufferedReader; 
import java.util.*;
import java.math.BigInteger; 


public class Main{
	public static FastReader fs = new FastReader();
	static int h,w,sx,sy,ex,ey;
	static char grid [][];
	static PrintWriter out = new PrintWriter(System.out);
	
	static boolean possible(int x,int y) {
		return (x >= 0 && y>= 0 && x<h && y<w && grid[x][y] == '.');
	}
	
	static class node implements Comparable<node>{
		int row,col,distance;
		node(int r,int c,int d){
			this.row = r;
			this.col = c;
			this.distance = d;
		}
		public int compareTo(node n) {
			return Integer.compare(distance, n.distance);
		}
	}
	
	static void solve() {
		h = fs.nextInt();w = fs.nextInt();
		sx = fs.nextInt()-1;sy = fs.nextInt()-1;
		ex = fs.nextInt()-1;ey = fs.nextInt()-1;
		grid = new char [h][w];
		for(int i = 0; i<h; i++) {
			char line [] = fs.next().toCharArray();
			for(int j = 0; j<w; j++) {
				grid[i][j] = line[j];
			}
		}
		PriorityQueue<node> pq = new PriorityQueue<>();
		int dist [][] = new int [h][w];
		for(int i = 0; i<h; i++)
			Arrays.fill(dist[i], 1_000_000_000);
		dist[sx][sy] = 0;
		pq.add(new node(sx,sy,0));
		while(!pq.isEmpty()) {
			node n = pq.remove();
			if(n.row == ex && n.col == ey) {
				out.println(n.distance);
				return;
			}
			if(possible(n.row+1,n.col) && dist[n.row+1][n.col] > n.distance) {
				dist[n.row+1][n.col] = n.distance;
				pq.add(new node(n.row+1,n.col,n.distance));
			}
			if(possible(n.row-1,n.col) && dist[n.row-1][n.col] > n.distance) {
				dist[n.row-1][n.col] = n.distance;
				pq.add(new node(n.row-1,n.col,n.distance));
			}
			if(possible(n.row,n.col+1) && dist[n.row][n.col+1] > n.distance) {
				dist[n.row][n.col+1] = n.distance;
				pq.add(new node(n.row,n.col+1,n.distance));
			}
			if(possible(n.row,n.col-1) && dist[n.row][n.col-1] > n.distance) {
				dist[n.row][n.col-1] = n.distance;
				pq.add(new node(n.row,n.col-1,n.distance));
			}
			
			for(int i = n.row-2; i <= n.row+2; i++) {
				for(int j = n.col-2; j <= n.col+2; j++) {
					if(possible(i,j) && dist[i][j] > n.distance+1){
						dist[i][j] = n.distance+1;
						pq.add(new node(i,j,n.distance+1));
					}
				}
			}
		}
		out.println(-1);
	}
	
	public static void main(String[] args) {
		Thread t = new Thread(null,null,"",1 << 28) {
			public void run() {
				int test_case = 1;
				//test_case = fs.nextInt();
				for(int cs = 1; cs <= test_case; cs++) {
					solve();
				}
				out.close();
			}
		};
		t.start();
		try {
			t.join();
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
	}
	static class FastReader 
    { 
        BufferedReader br; 
        StringTokenizer st; 
  
        public FastReader() 
        { 
            br = new BufferedReader(new
                     InputStreamReader(System.in)); 
        } 
  
        String next() 
        { 
            while (st == null || !st.hasMoreElements()) 
            { 
                try
                { 
                    st = new StringTokenizer(br.readLine()); 
                } 
                catch (IOException  e) 
                { 
                    e.printStackTrace(); 
                } 
            } 
            return st.nextToken(); 
        } 
  
        int nextInt() 
        { 
            return Integer.parseInt(next()); 
        } 
  
        long nextLong() 
        { 
            return Long.parseLong(next()); 
        } 
  
        double nextDouble() 
        { 
            return Double.parseDouble(next()); 
        } 
  
        String nextLine() 
        { 
            String str = ""; 
            try
            { 
                str = br.readLine(); 
            } 
            catch (IOException e) 
            { 
                e.printStackTrace(); 
            } 
            return str; 
        } 
        
        int [] readintarray(int n) {
        	int res [] = new int [n];
        	for(int i = 0; i<n; i++)res[i] = nextInt();
        	return res;
        }
        long [] readlongarray(int n) {
        	long res [] = new long [n];
        	for(int i = 0; i<n; i++)res[i] = nextLong();
        	return res;
        }
    } 
	
	static int ceil(int x,int y) {
		return (x % y == 0 ? x / y : (x / y +1));
	}
	
	static long ceil(long x,long y) {
		return (x % y == 0 ? x / y : (x / y +1));
	}
	
	static int max(int x,int y) {
		return Math.max(x, y);
	}
	
	static int min(int x,int y) {
		return Math.min(x, y);
	}
	
	static long max(long x,long y) {
		return Math.max(x, y);
	}
	
	static long min(long x,long y) {
		return Math.min(x, y);
	}
	
	static int min(int a []) {
		int x = 1_000_000_00_9;
		for(int i = 0; i<a.length; i++)x = min(x,a[i]);
		return x;
	}
	
	static int max(int a []) {
		int x = -1_000_000_00_9;
		for(int i = 0; i<a.length; i++)x = max(x,a[i]);
		return x;
	}
	
	static long min(long a []) {
		long x = (long)3e18;
		for(int i = 0; i<a.length; i++)x = min(x,a[i]);
		return x;
	}
	
	static long max(long a []) {
		long x = -(long)3e18;
		for(int i = 0; i<a.length; i++)x = max(x,a[i]);
		return x;
	}
	
	static int power(int x,int y) {
		int res = 1;
		while(y > 0) {
			if( y % 2 == 1)res = (res * x);
			y >>= 1;
            x = (x * x);
		}
		return res;
	}
	
	static long power(long x,long y) {
		long res = 1;
		while(y > 0) {
			if( y % 2 == 1)res = (res * x);
			y >>= 1;
            x = (x * x);
		}
		return res;
	}
	
	static long power(long x,long y,long mod) {
		long res = 1;
		x %= mod;
		while(y > 0) {
			if( y % 2 == 1)res = (res * x) % mod;
			y >>= 1;
            x = (x * x) % mod;
		}
		return res;
	}
	
	static void intsort(int [] a) {
		List<Integer> temp = new ArrayList<Integer>();
		for(int i = 0; i<a.length; i++)temp.add(a[i]);
		Collections.sort(temp);
		for(int i = 0; i<a.length; i++)a[i] = temp.get(i);
	}
	
	static void longsort(long [] a) {
		List<Long> temp = new ArrayList<Long>();
		for(int i = 0; i<a.length; i++)temp.add(a[i]);
		Collections.sort(temp);
		for(int i = 0; i<a.length; i++)a[i] = temp.get(i);
	}
	
	static void reverseintsort(int [] a) {
		List<Integer> temp = new ArrayList<Integer>();
		for(int i = 0; i<a.length; i++)temp.add(a[i]);
		Collections.sort(temp);
		Collections.reverse(temp);
		for(int i = 0; i<a.length; i++)a[i] = temp.get(i);
	}
	
	static void reverselongsort(long [] a) {
		List<Long> temp = new ArrayList<Long>();
		for(int i = 0; i<a.length; i++)temp.add(a[i]);
		Collections.sort(temp);
		Collections.reverse(temp);
		for(int i = 0; i<a.length; i++)a[i] = temp.get(i);
	}
	
	
	static void intervalsort(int a [],int start,int end) {
		ArrayList<Integer> temp = new ArrayList<>();
		for(int i = start; i<end; i++)
			temp.add(a[i]);
		Collections.sort(temp);
		for(int i = 0; i<temp.size(); i++)
			a[i+start] = temp.get(i);
	}
	
	static void intervalsort(long a [],int start,int end) {
		ArrayList<Long> temp = new ArrayList<>();
		for(int i = start; i<end; i++)
			temp.add(a[i]);
		Collections.sort(temp);
		for(int i = 0; i<temp.size(); i++)
			a[i+start] = temp.get(i);
	}
	
	static void reverseintervalsort(int a [],int start,int end) {
		ArrayList<Integer> temp = new ArrayList<>();
		for(int i = start; i<end; i++)
			temp.add(a[i]);
		Collections.sort(temp);
		Collections.reverse(temp);
		for(int i = 0; i<temp.size(); i++)
			a[i+start] = temp.get(i);
	}
	
	static void reverseintervalsort(long a [],int start,int end) {
		ArrayList<Long> temp = new ArrayList<>();
		for(int i = start; i<end; i++)
			temp.add(a[i]);
		Collections.sort(temp);
		Collections.reverse(temp);
		for(int i = 0; i<temp.size(); i++)
			a[i+start] = temp.get(i);
	}
	
	
	static class data{
		public long sum;
		
		data(long val){
		    this.sum = val;
		}
		
		data(){}
		
		data combine(data l, data r) {
		    data res = new data();
		    res.sum = l.sum + r.sum;
		    return res;
		}
	}
	
	static class Seg_Tree extends data{
		public int n;
		data [] seg;
		
		Seg_Tree(int sz){
			this.n = sz;
			seg = new data[4*n+4];
		}
		
		void build(long a[], int v, int tl, int tr) {
		    if (tl == tr) {
		        seg[v] = new data(a[tl]);
		    } else {
		        int tm = (tl + tr) / 2;
		        build(a, v*2, tl, tm);
		        build(a, v*2+1, tm+1, tr);
		        seg[v] = combine(seg[v*2],seg[v*2+1]);
		    }
		}

		void update(int v, int tl, int tr, int pos, long new_val) {
		    if (tl == tr) {
		        seg[v] = new data(new_val);
		    } else {
		        int tm = (tl + tr) / 2;
		        if (pos <= tm)
		            update(v*2, tl, tm, pos, new_val);
		        else
		            update(v*2+1, tm+1, tr, pos, new_val);
		        seg[v] = combine(seg[v*2],seg[v*2+1]);
		    }
		}
		
		data query(int v, int tl, int tr, int l, int r) {
		    if (l > r) 
		        return new data(0);
		    if (l == tl && r == tr) 
		        return seg[v];
		    int tm = (tl + tr) / 2;
		    return combine(query(v*2, tl, tm, l, min(r, tm)),query(v*2+1, tm+1, tr, max(l, tm+1), r));
		}
	}
	
	static class Bit_Tree{
		static int n;
		static int [] bit;
		
		Bit_Tree(int sz){
			Bit_Tree.n = sz;
			Bit_Tree.bit = new int[n+1];
		}
		
		static int child(int x) {
			return x + (x & (-x));
		}
		
		static int parent(int x) {
			return x - (x & (-x));
		}
		
		static void build(int [] a) {
			for(int i = 0; i<a.length; i++) {
				int start = i+1;
				while(start <= n) {
					bit[start] += a[i];
					start = child(start);
				}
			}
		}
		
		static void update(int idx,int new_val) {
			idx += 1;
			while(idx <= n) {
				bit[idx] += new_val;
				idx = child(idx);
			}
		}
		
		static int query(int right) {
			int res = 0;
			while(right > 0) {
				res += bit[right];
				right = parent(right);
			}
			return res;
		}
		
		static int query(int left,int right) {
			return query(right) - query(left-1);
		}
	}
	
	public static int gcd(int a, int b)  
    { 
        BigInteger b1 = BigInteger.valueOf(a); 
        BigInteger b2 = BigInteger.valueOf(b); 
        BigInteger gcd = b1.gcd(b2); 
            return gcd.intValue(); 
    } 
      
    public static long gcd(long a, long b)  
    { 
        BigInteger b1 = BigInteger.valueOf(a); 
        BigInteger b2 = BigInteger.valueOf(b); 
        BigInteger gcd = b1.gcd(b2); 
            return gcd.longValue(); 
    } 
}