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())
    
    sy -= 1
    sx -= 1
    gy -= 1
    gx -= 1
    
    grid = []
    for _ in range(R):
        line = sys.stdin.readline().strip()
        grid.append(list(line))
    
    distance = [[-1 for _ in range(C)] for _ in range(R)]
    distance[sy][sx] = 0
    
    queue = deque()
    queue.append((sy, sx))
    
    directions = [(-1, 0), (1, 0), (0, -1), (0, 1)]
    
    while queue:
        y, x = queue.popleft()
        if y == gy and x == gx:
            print(distance[y][x])
            return
        for dy, dx in directions:
            new_y = y + dy
            new_x = x + dx
            if 0 <= new_y < R and 0 <= new_x < C:
                if grid[new_y][new_x] == '.' and distance[new_y][new_x] == -1:
                    distance[new_y][new_x] = distance[y][x] + 1
                    queue.append((new_y, new_x))

if __name__ == "__main__":
    main()