#include <tuple>
#include <algorithm>
#include <vector>
#include <iostream>
using namespace std;

int main() {
    int h, w, n; cin >> h >> w >> n;
    vector C(h, vector<int>(w));
    for (int i = 0; i < h; i++)
        for (int j = 0; j < w; j++) {
            int c; cin >> c;
            C[i][j] = c - 1;
        }
    vector<vector<pair<int, int> > > adj(n);
    for (int c = 1; c < n; c++) adj[c-1].emplace_back(c, 0);
    for (int i = 0; i < h; i++)
        for (int j = 0; j < w; j++) {
            if (i > 0) {
                if (const int a = C[i-1][j], b = C[i][j]; a != b)
                    adj[min(a, b)].emplace_back(max(a, b), 1);
            }
            if (j > 0) {
                if (const int a = C[i][j-1], b = C[i][j]; a != b)
                    adj[min(a, b)].emplace_back(max(a, b), 1);
            }
        }
    vector<int> dp(n, 1);
    for (int i = 0; i < n; i++)
        for (auto [j, d] : adj[i]) dp[j] = max(dp[j], dp[i] + d);
    cout << dp.back() << '\n';
}