import sys
from collections import deque

def main():
    R, C = map(int, sys.stdin.readline().split())
    sy, sx = map(int, sys.stdin.readline().split())
    gy, gx = map(int, sys.stdin.readline().split())
    
    # Convert to 0-based indices
    sy -= 1
    sx -= 1
    gy -= 1
    gx -= 1
    
    # Read the maze
    maze = [sys.stdin.readline().strip() for _ in range(R)]
    
    # Initialize distance matrix with -1 (unvisited)
    distance = [[-1 for _ in range(C)] for _ in range(R)]
    distance[sy][sx] = 0  # Starting point
    
    # Directions: up, down, left, right
    dy = [-1, 1, 0, 0]
    dx = [0, 0, -1, 1]
    
    q = deque()
    q.append((sy, sx))
    
    while q:
        y, x = q.popleft()
        
        # Check if current position is the goal
        if y == gy and x == gx:
            print(distance[y][x])
            return
        
        # Explore all four directions
        for i in range(4):
            ny = y + dy[i]
            nx = x + dx[i]
            
            # Check if the next position is within bounds, is a path, and unvisited
            if 0 <= ny < R and 0 <= nx < C:
                if maze[ny][nx] == '.' and distance[ny][nx] == -1:
                    distance[ny][nx] = distance[y][x] + 1
                    q.append((ny, nx))
    
    # If somehow the loop exits without returning (though problem states a path exists)
    print(-1)

if __name__ == "__main__":
    main()