#include <iostream>
#include <algorithm>
#include <iomanip>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <tuple>
#include <cmath>
#include <numeric>
#include <functional>
#include <cassert>

#define debug_value(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << #x << "=" << x << endl;
#define debug(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << x << endl;

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

using namespace std;
typedef long long ll;

struct UnionFind {
    vector<int> data;
    UnionFind(int size) : data(size, -1) {}
    bool unionSet(int x, int y) {
        x = root(x); y = root(y);
        if (x != y) {
        if (data[y] < data[x]) swap(x, y);
        data[x] += data[y]; data[y] = x;
        }
        return x != y;
    }
    bool findSet(int x, int y) {
        return root(x) == root(y);
    }
    int root(int x) {
        return data[x] < 0 ? x : data[x] = root(data[x]);
    }
    int size(int x) {
        return -data[root(x)];
    }
};

bool topological_sort(vector<vector<int>> g, vector<int> &order){
    int n = g.size();
    order.clear();
    vector<bool> used(n, false);
    function<void(int)> dfs = [&](int v){
        used[v] = true;
        for(int to : g[v]){
            if(!used[to]) dfs(to);
        }
        order.push_back(v);
    };
    for(int v = 0; v < n; v++){
        if(!used[v]) dfs(v);
    }
    reverse(order.begin(), order.end());
    vector<int> inv_order(n);
    for(int i = 0; i < n; i++) inv_order[order[i]] = i;
    for(int v = 0; v < n; v++){
        for(int u : g[v]){
            if(inv_order[v] > inv_order[u]) return false;
        }
    }
    return true;
}

template<typename T>
class Compress{
    public:
    vector<T> data;
    int offset;
    Compress(vector<T> data_, int offset=0): offset(offset){
        set<T> st;
        for(T x: data_) st.insert(x);
        for(T x: st) data.push_back(x);
    };
    int operator[](T x) {
        auto p = lower_bound(data.begin(), data.end(), x);
        assert(x == *p);
        return offset+(p-data.begin());
	}
    T inv(int x){
        return data[x-offset];
    }
    int size(){
        return data.size();
    }
};

using P = pair<int, int>;

int dh[4] = {0, 0, -1, 1};
int dw[4] = {-1, 1, 0, 0};



int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << setprecision(10) << fixed;
    int h, w, n; cin >> h >> w >> n;
    vector<vector<int>> c(h, vector<int>(w));
    vector<vector<int>> ans(h, vector<int>(w));
    map<int, vector<P>> mp;
    for(int i = 0; i < h; i++){
        for(int j = 0; j < w; j++){
            cin >> c[i][j];
            mp[c[i][j]].push_back(P(i, j));
        }
    }
    auto is_in_field = [&](int i, int j){
        return i >= 0 && i < h && j >= 0 && j < w;
    };
    int cur = 1;
    for(int i = 1; i <= n; i++){
        int tmp = cur;
        for(auto [x, y]: mp[i]){
            int p = cur;
            for(int k = 0; k < 4; k++){
                int x_to = x+dh[k];
                int y_to = y+dw[k];
                if(!is_in_field(x_to, y_to)) continue;
                if(c[x_to][y_to] == n) continue;
                chmax(p, ans[x_to][y_to]+1);
            }
            chmax(tmp, p);
        }
        for(auto [x, y]: mp[i]) ans[x][y] = tmp;
        cur = tmp;
    }
    cout << cur << endl;
}