#exec({'RUBY_THREAD_VM_STACK_SIZE'=>'100000000'},'/usr/bin/ruby', $0) if !ENV['RUBY_THREAD_VM_STACK_SIZE']
require 'prime'

def inpf() a=gets.chomp.split(" ").map(&:to_f)end

def inps() a=gets.chomp.split(" ")end

def copy(a) Marshal.load(Marshal.dump(a)) end

def kaijo(n,r = 10**9+7)(n < 2)? 1 : (2..n).inject{|memo,u|memo=(memo*u)%r} end

def na(n,d=0) Array.new(n,d)end

def na2(n,m,d=0) Array.new(n){Array.new(m,d)}end

def na3(n,m,l,d=0) Array.new(n){Array.new(m){Array.new(l,d)}}end

def inp() a=gets.chomp.split(" ").map(&:to_i)end

def r_up(a, b) (a+b-1)/b end

def sum(a) a.inject(:+) end

def big(a,b) return (a>b)? a:b end

def small(a,b) return (a<b)? a:b end

#exec({'RUBY_THREAD_VM_STACK_SIZE'=>'100000000'},'/usr/bin/ruby', $0) if !ENV['RUBY_THREAD_VM_STACK_SIZE']
require 'prime'

def inpf() a=gets.chomp.split(" ").map(&:to_f)end

def inps() a=gets.chomp.split(" ")end

def copy(a) Marshal.load(Marshal.dump(a)) end

def kaijo(n,r = 10**9+7)(n < 2)? 1 : (2..n).inject{|memo,u|memo=(memo*u)%r} end

def na(n,d=0) Array.new(n,d)end

def na2(n,m,d=0) Array.new(n){Array.new(m,d)}end

def na3(n,m,l,d=0) Array.new(n){Array.new(m){Array.new(l,d)}}end

def inp() a=gets.chomp.split(" ").map(&:to_i)end

def r_up(a, b) (a+b-1)/b end

def sum(a) a.inject(:+) end

def big(a,b) return (a>b)? a:b end

def small(a,b) return (a<b)? a:b end

h,w = inp
c = inp
d = inp
c = [c[0]-1,c[1]-1]
d = [d[0]-1, d[1]-1]
mem = na2(h,w,false)
h.times do |i|
  s = gets.chomp
  s.split("").each.with_index do |c ,j|
    mem[i][j] = (c == "#")
  end
end
deque = [[c[0],c[1],0]]

while deque.size > 0
  y,x,c = deque.pop
  if([y,x] == d)
    puts c
    exit
  end
  mem[y][x] = true
  ((y-2)..(y+2)).each do |yy|
    next if yy < 0
    break if yy >= h
    ((y-2)..(y+2)).each do |xx|
      next if xx < 0
      break if xx >= w
      next if mem[yy][xx]
      if(x.abs + y.abs == 1)
        deque.push([yy,xx,c])
      else
        deque.unshift([yy,xx,c+1])
      end
    end
  end
end
p -1
