from heapq import *

h, w = map(int, input().split())
A = [list(map(int, input().split())) for _ in range(h)]

hq1 = [(A[0][0], 0, 0)]
hq2 = [(A[h - 1][w - 1], h - 1, w - 1)]
used = [[False] * w for _ in range(h)]
used1 = [[False] * w for _ in range(h)]
used2 = [[False] * w for _ in range(h)]
ans = 0
used1[0][0] = True
used2[h - 1][w - 1] = True

di = [1, 0, -1, 0]
dj = [0, 1, 0, -1]

while 1:
    ans += 1
    a, i, j = heappop(hq1)
    used[i][j] = True
    for k in range(4):
        ni, nj = i + di[k], j + dj[k]
        if ni == -1 or ni == h or nj == -1 or nj == w:
            continue
        if not used1[ni][nj]:
            if used[ni][nj]:
                print(ans - 2)
                exit()
            heappush(hq1, (A[ni][nj], ni, nj))
            used1[ni][nj] = True

    hq1, hq2 = hq2, hq1
    used1, used2 = used2, used1