dxdy=zip([-1,0,1,0],[0,1,0,-1])
def kadomatsu(a,b,c):
    if a==0 or b==0:
        return True
    else:
        if (a!=b and b!=c and c!=a) and not (a<b<c or a>b>c):
            return True
        else:
            return False
W,H=map(int,raw_input().split())
M=[map(int,raw_input().split()) for _ in xrange(H)]
que=[[0,0,0,0]]
while que:
    [x,y,bfr,count]=que.pop(0)
    cur=M[y][x]
    if x==W-1 and y==H-1:
        print count
        exit()
    for dx,dy in dxdy:
        nx,ny=x+dx,y+dy
        if not(0<=nx<W and 0<=ny<H):continue
        aft=M[ny][nx]
        if not kadomatsu(bfr,cur,aft):continue
        que.append([nx,ny,cur,count+1])
print -1