from collections import deque

def main():
    import sys
    input = sys.stdin.read
    data = input().split()
    
    idx = 0
    R = int(data[idx])
    idx += 1
    C = int(data[idx])
    idx += 1
    
    sy = int(data[idx]) - 1
    idx += 1
    sx = int(data[idx]) - 1
    idx += 1
    
    gy = int(data[idx]) - 1
    idx += 1
    gx = int(data[idx]) - 1
    idx += 1
    
    grid = []
    for i in range(R):
        grid.append(data[idx])
        idx += 1
    
    if sy == gy and sx == gx:
        print(0)
        return
    
    directions = [ (-1, 0), (1, 0), (0, -1), (0, 1) ]
    
    dist = [ [ -1 for _ in range(C) ] for _ in range(R) ]
    q = deque()
    q.append( (sy, sx) )
    dist[sy][sx] = 0
    
    while q:
        y, x = q.popleft()
        for dy, dx in directions:
            ny = y + dy
            nx = x + dx
            if 0 <= ny < R and 0 <= nx < C:
                if grid[ny][nx] == '.' and dist[ny][nx] == -1:
                    dist[ny][nx] = dist[y][x] + 1
                    if ny == gy and nx == gx:
                        print(dist[ny][nx])
                        return
                    q.append( (ny, nx) )
    
    # According to problem statement, it's guaranteed to reach, so no need for this
    print(-1)

if __name__ == "__main__":
    main()