import sys
input = sys.stdin.readline

H, W, N = map(int, input().split())
G = [[] for i in range(N)]
for i in range(H):
    C = list(map(int, input().split()))
    for j in range(W):
        G[C[j] - 1].append((i, j))

inf = 10 ** 18
temp = [[-inf] * W for i in range(H)]
dx = [1, 0, -1, 0]
dy = [0, 1, 0, -1]
for i in range(N):
    dic = dict()
    for x, y in G[i]:
        val = 0
        for k in range(4):
            nx = x + dx[k]
            ny = y + dy[k]
            if nx < 0 or nx > H - 1 or ny < 0 or ny > W - 1:
                continue
            val = max(val, temp[nx][ny] + 1)
        dic[(x, y)] = val

    for x, y in G[i]:
        temp[x][y] = dic[(x, y)]

ans = 0
for i in range(H):
    ans = max(ans, max(temp[i]))

print(ans + 1)