head = 0
q = []

def isempty():
    return head == len(q)

def push(val):
    q.append(val)

def pop():
    global head
    head += 1

def front():
    return q[head]

n, m = map(int, input().split())

s = list(map(int, input().split()))
t = list(map(int, input().split()))

g = []

for i in range(n):
    g.append(str(input()))

d = []

for i in range(n):
    d.append([])
    for j in range(m):
        d[i].append(-1)

dx = [0, -1, 0, 1]
dy = [-1, 0, 1, 0]

d[s[0]][s[1]] = 0
push(s)

def check(x, y):
    return 0 <= x and x < n and 0 <= y and y < m and g[x][y] != 'X'

if (not check(s[0], s[1])):
    print('INF')
    exit()

if (not check(t[0], t[1])):
    print('INF')
    exit()

ans = []

while (not isempty()):
    u = front()
    x = u[0]
    y = u[1]
    pop()
    for i in range(4):
        nx = x + dx[i]
        ny = y + dy[i]
        if (check(nx, ny)):
            if (d[nx][ny] == -1):
                d[nx][ny] = d[x][y] + 1
                push((nx, ny))

if (d[t[0]][t[1]] == -1):
    print('INF')
    exit()

print(d[t[0]][t[1]])