import sys

# sys.setrecursionlimit(200005)
# sys.set_int_max_str_digits(200005)
int1 = lambda x: int(x)-1
pDB = lambda *x: print(*x, end="\n", file=sys.stderr)
p2D = lambda x: print(*x, sep="\n", end="\n\n", file=sys.stderr)
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def SI(): return sys.stdin.readline().rstrip()

dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
# dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
# inf = -1-(-1 << 31)
inf = -1-(-1 << 62)

# md = 10**9+7
md = 998244353

from heapq import *

h,w=LI()
aa=LLI(h)
tt=[[-1]*w for _ in range(h)]

a2ij={}
for i in range(h):
    for j,a in enumerate(aa[i]):
        a2ij[a]=(i,j)

hp=[[],[]]
st=[set(),set()]
tt[0][0]=1
tt[-1][-1]=0
st[1].add(aa[0][0])
st[0].add(aa[-1][-1])

k=1
for i,j in [(0,0),(h-1,w-1)]:
    for di, dj in dij:
        ni, nj = i+di, j+dj
        if ni < 0 or nj < 0 or ni >= h or nj >= w: continue
        st[k].add(aa[ni][nj])
        heappush(hp[k],aa[ni][nj])
    k^=1
# print(hp,st)

ans=0
k=1
while 1:
    a=heappop(hp[k])
    i,j=a2ij[a]
    tt[i][j]=k
    ans+=1
    for di, dj in dij:
        ni, nj = i+di, j+dj
        if ni < 0 or nj < 0 or ni >= h or nj >= w: continue
        if tt[ni][nj]==k^1:
            print(ans)
            exit()
        if aa[ni][nj] in st[k]:continue
        st[k].add(aa[ni][nj])
        heappush(hp[k],aa[ni][nj])
    k^=1
    # print(k,hp,st)