from heapq import heapify,heappop,heappush

h,w=map(int,input().split())

a=[list(map(int,input().split())) for i in range(h)]

colored0=set([(0,0)])
colored1=set([(h-1,w-1)])
ad0=set([(0,0),(0,1),(1,0)])
ad1=set([(h-1,w-1),(h-2,w-1),(h-1,w-2)])
ad=[ad0,ad1]
que0=[]
que1=[]
heappush(que0,(a[0][1],0,1))
heappush(que0,(a[1][0],1,0))
heappush(que1,(a[h-1][w-2],h-1,w-2))
heappush(que1,(a[h-2][w-1],h-2,w-1))
que=[que0,que1]
colored=[colored0,colored1]
walk=[
    (1,0),
    (-1,0),
    (0,1),
    (0,-1),
]
def inside(y,x):
    return 0<=y<h and 0<=x<w

for i in range(h*w):
    t_que=que[i%2]
    t_colored=colored[i%2]
    o_colored=colored[(i%2)^1]
    t_ad=ad[i%2]
    while t_que:
        _,y,x=heappop(t_que)
        if (y,x) not in t_colored:
            break
    t_colored.add((y,x))
    # 隣がo_coloredで塗られている場合exit
    for iy,ix in walk:
        ny,nx=iy+y,ix+x
        if (ny,nx) in o_colored:
            print(i+1)
            exit()

    for iy,ix in walk:
        ny,nx=iy+y,ix+x
        if inside(ny,nx):
            if not (ny,nx) in t_ad:
                t_ad.add((ny,nx))
                heappush(t_que,(a[ny][nx],ny,nx))