#include <bits/stdc++.h>
using namespace std;
vector<int> dx = {1, 0, -1, 0};
vector<int> dy = {0, 1, 0, -1};
int main(){
  int H, W, N;
  cin >> H >> W >> N;
  vector<vector<int>> C(H, vector<int>(W));
  for (int i = 0; i < H; i++){
    for (int j = 0; j < W; j++){
      cin >> C[i][j];
      C[i][j]--;
    }
  }
  vector<vector<int>> px(N), py(N);
  vector<int> cnt(N);
  for (int i = 0; i < H; i++){
    for (int j = 0; j < W; j++){
      px[C[i][j]].push_back(i);
      py[C[i][j]].push_back(j);
      cnt[C[i][j]]++;
    }
  }
  vector<int> dp(N);
  int ans = 1;
  for (int i = 0; i < N; i++){
    dp[i] = ans;
    for (int j = 0; j < cnt[i]; j++){
      int x = px[i][j];
      int y = py[i][j];
      for (int k = 0; k < 4; k++){
        int x2 = x + dx[k];
        int y2 = y + dy[k];
        if (0 <= x2 && x2 < H && 0 <= y2 && y2 < W){
          if (C[x2][y2] < i){
            dp[i] = max(dp[i], dp[C[x2][y2]] + 1);
          }
        }
      }
    }
    ans = max(ans, dp[i]);
  }
  cout << ans << endl;
}