def g;gets.split.map(&:to_i)end
def isKadomatsuSequence a
  a.minmax.index(a[1])&&a.uniq==a
end
w,h=g
m=(1..h).map{g<<0}<<[0]*w
q=[[0,0,[0,0,m[0][0]],0]]
memo={}
p (while q[0]
  y,x,l,s=q.shift
  next if memo[[y,x,l]]
  memo[[y,x,l]]
  break s if [y,x]==[h-1,w-1]
  [[y+1,x],[y,x+1],[y-1,x],[y,x-1]].each{|dy,dx|
    dl=l[1,2]+[m[dy][dx]]
    if m[dy][dx]>0 && (dl[0]==0 || isKadomatsuSequence(dl))
      q<<[dy,dx,dl,s+1]
    end
  }
end)||-1