#include <vector>
#include <list>
#include <map>
#include <set>
#include <unordered_set>
#include <unordered_map>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <queue>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>
#include <fstream>
#include <cstdio>
#include <climits>
#include <complex>
#include <cstdint>
#include <tuple>

#define M_PI       3.14159265358979323846

using namespace std;

//conversion
//------------------------------------------
inline int toInt(string s) { int v; istringstream sin(s); sin >> v; return v; }
template<class T> inline string toString(T x) { ostringstream sout; sout << x; return sout.str(); }
inline int readInt() { int x; scanf("%d", &x); return x; }

//typedef
//------------------------------------------
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef pair<int, PII> TIII;
typedef long long LL;
typedef unsigned long long ULL;
typedef vector<LL> VLL;
typedef vector<VLL> VVLL;

//container util

//------------------------------------------
#define ALL(a)  (a).begin(),(a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define MP make_pair
#define SZ(a) int((a).size())
#define SQ(a) ((a)*(a))
#define EACH(i,c) for(typeof((c).begin()) i=(c).begin(); i!=(c).end(); ++i)
#define EXIST(s,e) ((s).find(e)!=(s).end())
#define SORT(c) sort((c).begin(),(c).end())

//repetition
//------------------------------------------
#define FOR(i,s,n) for(int i=s;i<(int)n;++i)
#define REP(i,n) FOR(i,0,n)
#define MOD 1000000007

#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define trav(a, x) for(auto& a : x)
#define all(x) x.begin(), x.end()
#define sz(x) (int)(x).size()

enum FACE { TOP, BOTTOM, FRONT, BACK, LEFT, RIGHT };
template <class T>
class dice {
public:
    dice() {
        id[TOP] = 0; id[FRONT] = 1; id[LEFT] = 2;
        id[RIGHT] = 3; id[BACK] = 4; id[BOTTOM] = 5;
    }
    T& operator[] (FACE f) { return var[id[f]]; }
    const T& operator[] (FACE f) const { return var[id[f]]; }
    bool operator==(const dice<T>& b) const {
        const dice<T> &a = *this;
        return a[TOP] == b[TOP] && a[BOTTOM] == b[BOTTOM] &&
               a[FRONT] == b[FRONT] && a[BACK] == b[BACK] &&
               a[LEFT] == b[LEFT] && a[RIGHT] == b[RIGHT];
    }
    void roll_x() { roll(TOP, BACK, BOTTOM, FRONT); }
    void roll_y() { roll(TOP, LEFT, BOTTOM, RIGHT); }
    void roll_z() { roll(FRONT, RIGHT, BACK, LEFT); }
    vector<dice> all_rolls() {
        vector<dice> ret;
        for (int k = 0; k < 6; (k&1?roll_y():roll_x()),++k)
            for (int i = 0; i < 4; roll_z(), ++i)
                ret.push_back(*this);
        return ret;
    }
    bool equivalent_to(const dice& di) {
        for (int k = 0; k < 6; (k&1?roll_y():roll_x()),++k)
            for (int i = 0; i < 4; roll_z(), ++i)
                if (*this == di) return true;
        return false;
    }
private:
    void roll(FACE a, FACE b, FACE c, FACE d) {
        T tmp = id[a];
        id[a] = id[b]; id[b] = id[c];
        id[c] = id[d]; id[d] = tmp;
    }
    T var[6];
    int id[6];
};

struct Edge {
    int to, cost;
    Edge(int to, int cost): to(to), cost(cost) {}
};

typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<vector<Edge>> AdjList;
AdjList graph;
#define chmin(x,y) x=min(x,y)
#define chmax(x,y) x=max(x,y)
const int INF = 100000000;

int GCD(int a, int b){
    if(a < b) swap(a, b);
    if(b == 0) return a;
    return GCD(b, a%b);
}

bool cmp(const pii& a, const pii& b){
    if(a.first == b.first){
        return a.second < b.second;
    }
    return a.first < b.first;
}
int h, w, c;
int dxy[5] = {-1, 0, 1, 0, -1};
int maxV;
void dfs(int y, int x, int turn, int p[10][10]) {
    if (turn == 5) {
            queue<pii> q;
            q.push({y, x});int cnt=0;
            if(p[y][x] == c)  cnt++;

            bool used[10][10];
            REP(i, 10) REP(j, 10) used[i][j] = false;
            used[y][x] = true;
            while (q.size()) {
                pii P = q.front();
                q.pop();
                int Y = P.first;
                int X = P.second;
                for (int i = 0; i < 4; ++i) {
                    int ny = Y + dxy[i],
                            nx = X + dxy[i + 1];
                    if (ny >= 0 && ny < h && nx >= 0 && nx < w && !used[ny][nx]) {
                        if (p[ny][nx] == c) {
                            used[ny][nx] = true;
                            q.push({ny, nx});
                            cnt++;
                        }
                    }
                }
            }

        maxV = max(maxV, cnt);

        return ;
    }


    for(int i=1; i<=6; ++i){
        queue<pair<int, int>> q;

        q.push({y, x});
        int t = p[y][x]; //変更前の色


        if(t==i) continue;
        int np[10][10];bool passed[10][10];
        REP(j, 10)REP(k, 10) {
                np[j][k] = p[j][k];
                passed[j][k]=false;
            }
        passed[y][x] = true;

        while(q.size()){
            pii P = q.front();
            q.pop();

            int Y = P.first, X = P.second;
            for(int j=0; j<4; ++j){
                int ny = Y + dxy[j],
                nx = X + dxy[j+1];
                if(ny>=0 && ny<h && nx>=0&& nx<w && !passed[ny][nx] && p[ny][nx] == p[y][x]){
                    passed[ny][nx] = true;
                    q.push({ny, nx});
                }
            }
        }
        for(int j=0; j<h; ++j){
            for(int k=0; k<w; ++k){
                if(passed[j][k]){
                    np[j][k] = i;
                }
            }
        }
        dfs(y, x, turn+1, np);
    }
}
int main() {
    //cout << fixed << setprecision(15);


    while(cin >> h >> w >> c){
        if(h==0 && w==0 && c==0) break;
        maxV = 1;
        int p[10][10];
        REP(i, 10) REP(j, 10) p[i][j]=0;
        REP(i, h) REP(j, w) cin >> p[i][j];


        bool cused[10];
        for(int i=0; i<10; ++i) cused[i] = false;
        dfs(0, 0, 0, p);

        cout << maxV << endl;
    }

    return 0;
}


Measured memory_bytes: 3116