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
    
    grid = [sys.stdin.readline().strip() for _ in range(R)]
    
    # Initialize distance matrix with -1 (unvisited)
    dist = [[-1 for _ in range(C)] for _ in range(R)]
    dist[sy][sx] = 0
    
    # Directions: up, down, left, right
    directions = [(-1, 0), (1, 0), (0, -1), (0, 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(dist[y][x])
            return
        
        for dy, dx in directions:
            ny = y + dy
            nx = x + dx
            
            # Check if the new position is within bounds
            if 0 <= ny < R and 0 <= nx < C:
                # Check if the cell is accessible and not visited
                if grid[ny][nx] == '.' and dist[ny][nx] == -1:
                    dist[ny][nx] = dist[y][x] + 1
                    q.append((ny, nx))
    
    # The problem states that the goal is reachable, so this line is theoretically unreachable
    print(-1)

if __name__ == "__main__":
    main()