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

// The main method must be in a class named "Main".
class Main {
    static class Vec2{
        int y;
        int x;

        Vec2(int y, int x) {
            this.y = y;
            this.x = x;
    }
}
    


    static int[] dy = {-1, 0, 1, 0};
    static int[] dx = {0, 1, 0, -1};
    
    static final int INF = -1; 

    static int solveMaze(int h, int w, int[][] maze, int sy, int sx, int gy, int gx) {
        Queue<Vec2> q = new ArrayDeque<>();
        q.add(new Vec2(sy, sx));
        int[][] distance = new int[h][w];

        for (int i=0; i<h; i++) {
            for (int j=0; j<w; j++) {
                distance[i][j] = INF;
            }
        }
        distance[sy][sx] = 0;
        while (!q.isEmpty()) {
            Vec2 cur = q.poll();
            for (int i=0; i<4; i++) {
                int ny = cur.y + dy[i];
                int nx = cur.x + dx[i];

                if (0 <= ny && ny < h && 0<= nx && nx < w) {
                    if (maze[ny][nx] == 0 && distance[ny][nx] == INF) {
                        distance[ny][nx] = distance[cur.y][cur.x] + 1;
                        q.add(new Vec2(ny, nx));
                    }
                }
            }
        }
        return distance[gy][gx];
    }
    
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int h = sc.nextInt(), w = sc.nextInt(); 
        int[][] maze = new int[h][w]; 
        for (int i=0; i<h; i++) {
            String line = sc.next();
            for (int j=0; j<w; j++) {
                maze[i][j] = line.charAt(j) == '#' ? 1 : 0;
            }
        }
        int sy = sc.nextInt() - 1, sx = sc.nextInt() -1; 
        int gy = sc.nextInt() - 1, gx = sc.nextInt() -1;

        int d = solveMaze(h, w, maze, sy, sx, gy, gx);
        System.out.println(d);
        
    }
}