from heapq import heappop, heappush


H, W = map(int, input().split())
A = [list(map(int, input().split())) for _ in range(H)]
di, dj = [1, 0, -1, 0], [0, 1, 0, -1]
hq1 = []
hq2 = []
C = [[-1] * W for _ in range(H)]
C[0][0] = 0
C[-1][-1] = 1
add1 = [[False] * W for _ in range(H)]
add2 = [[False] * W for _ in range(H)]
for d in range(4):
    ni, nj = di[d], dj[d]
    if 0 <= ni < H and 0 <= nj < W:
        add1[ni][nj] = True
        heappush(hq1, (A[ni][nj], ni, nj))
for d in range(4):
    ni, nj = H - 1 + di[d], W - 1 + dj[d]
    if 0 <= ni < H and 0 <= nj < W:
        add2[ni][nj] = True
        heappush(hq2, (A[ni][nj], ni, nj))

ans = 1
while hq1 and hq2:
    if ans & 1:
        v, i, j = heappop(hq1)
        C[i][j] = 0
        for d in range(4):
            ni, nj = i + di[d], j + dj[d]
            if 0 <= ni < H and 0 <= nj < W and C[ni][nj] != -1 and C[ni][nj] != C[i][j]:
                print(ans)
                exit()
            if 0 <= ni < H and 0 <= nj < W and C[ni][nj] == -1 and not add1[ni][nj]:
                add1[ni][nj] = True
                heappush(hq1, (A[ni][nj], ni, nj))
    else:
        v, i, j = heappop(hq2)
        C[i][j] = 1
        for d in range(4):
            ni, nj = i + di[d], j + dj[d]
            if 0 <= ni < H and 0 <= nj < W and C[ni][nj] != -1 and C[ni][nj] != C[i][j]:
                print(ans)
                exit()
            if 0 <= ni < H and 0 <= nj < W and C[ni][nj] == -1 and not add2[ni][nj]:
                add2[ni][nj] = True
                heappush(hq2, (A[ni][nj], ni, nj))
    ans += 1
assert 0