from collections import deque

# Read input
R, C = map(int, input().split())
sy, sx = map(int, input().split())
gy, gx = map(int, input().split())

# Convert to 0-based indices
sy -= 1
sx -= 1
gy -= 1
gx -= 1

# Read grid
grid = [input().strip() for _ in range(R)]

# Directions: up, down, left, right
dx = [-1, 1, 0, 0]
dy = [0, 0, -1, 1]

# Initialize distance array
dist = [[-1] * C for _ in range(R)]
q = deque()

# Start BFS from the start position
dist[sy][sx] = 0
q.append((sy, sx))

found = False

while q and not found:
    y, x = q.popleft()
    
    # Check if current position is the goal
    if y == gy and x == gx:
        print(dist[y][x])
        found = True
        break
    
    # 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
        if 0 <= ny < R and 0 <= nx < C:
            # Check if the cell is passable and not visited
            if grid[ny][nx] == '.' and dist[ny][nx] == -1:
                dist[ny][nx] = dist[y][x] + 1
                q.append((ny, nx))