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 = [sys.stdin.readline().strip() for _ in range(R)]
    
    distance = [[-1 for _ in range(C)] for _ in range(R)]
    distance[sy][sx] = 0
    
    q = deque()
    q.append((sy, sx))
    
    directions = [(-1, 0), (1, 0), (0, -1), (0, 1)]
    
    while q:
        y, x = q.popleft()
        if y == gy and x == gx:
            print(distance[y][x])
            return
        for dy, dx in directions:
            ny = y + dy
            nx = x + dx
            if 0 <= ny < R and 0 <= nx < C:
                if grid[ny][nx] == '.' and distance[ny][nx] == -1:
                    distance[ny][nx] = distance[y][x] + 1
                    q.append((ny, nx))
    
if __name__ == "__main__":
    main()