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 = []
    for _ in range(R):
        line = sys.stdin.readline().strip()
        maze.append(list(line))
    
    # 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
    dy = [-1, 1, 0, 0]
    dx = [0, 0, -1, 1]
    
    q = deque()
    q.append((sy, sx))
    
    while q:
        y, x = q.popleft()
        current_dist = dist[y][x]
        
        for i in range(4):
            ny = y + dy[i]
            nx = x + dx[i]
            
            if 0 <= ny < R and 0 <= nx < C:
                if maze[ny][nx] == '.' and dist[ny][nx] == -1:
                    dist[ny][nx] = current_dist + 1
                    q.append((ny, nx))
                    
                    if ny == gy and nx == gx:
                        print(dist[ny][nx])
                        return
    
    # According to the problem statement, the path always exists.
    print(dist[gy][gx])

if __name__ == "__main__":
    main()