#include <cassert>

#include <cctype>
#include <cerrno>
#include <cfloat>
#include <ciso646>
#include <climits>
#include <clocale>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <ccomplex>
#include <cfenv>
#include <cinttypes>
#include <cstdbool>
#include <cstdint>
#include <ctgmath>
#include <cwchar>
#include <cwctype>

// C++
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>
#include <array>
#include <atomic>
#include <chrono>
#include <condition_variable>
#include <forward_list>
#include <future>
#include <initializer_list>
#include <mutex>
#include <random>
#include <ratio>
#include <regex>
#include <scoped_allocator>
#include <system_error>
#include <thread>
#include <tuple>
#include <typeindex>
#include <type_traits>
#include <unordered_map>
#include <unordered_set>
// #include <boost/foreach.hpp>
// #include <boost/range/algorithm.hpp>
#define rep(i,j,k) for(int i=(int)j;i<(int)k;i++)
#define ll long long
#define Sort(v) sort(all(v))
//#define INF 1e9
#define LINF 1e18
#define END return 0
#define pb push_back
#define se second
#define fi first
#define pb push_back
#define all(v) (v).begin() , (v).end()
#define MP make_pair
#define int long long
using namespace std;
int day[12]={31,28,31,30,31,30,31,31,30,31,30,31};
// int dx[]={0,1,0,-1};
// int dy[]={1,0,-1,0};
struct edge{int to,cost;};
//typedef pair<int,int> P;

const long long MOD=1000000007LL;
bool isupper(char c){if('A'<=c&&c<='Z')return 1;return 0;}
bool islower(char c){if('a'<=c&&c<='z')return 1;return 0;}
bool isPrime(int x){if(x==1)return 0;if(x==2)return 1;if(x%2==0)return 0;for(int i=3;i*i<=x;i++)if(x%i==0)return 0;return 1;}
bool iskaibun(string s){for(int i=0;i<s.size()/2;i++)if(s[i]!=s[s.size()-i-1])return 0;return 1;}
bool isnumber(char c){return ('0'<=c&&c<='9');}
bool isalpha(char c){return (isupper(c)||islower(c));}
template<typename T> 
void print(vector<T> v){
    for(int i=0;i<v.size();i++){
        if(i)cout<<" ";
        cout<<v[i];
    }
    cout<<endl;
}

template<typename T>
void printendl(vector<T> v){
    for(auto date:v)cout<<date<<endl;
}

template<typename T>
void printvv(vector<vector<T>> v){
    for(int i=0;i<v.size();i++){
        for(int j=0;j<v[i].size();j++){
            if(j)cout<<" ";
            cout<<v[i][j];
        }
        cout<<endl;
    }
}
int gcd(int a,int b){
    if(a<b)swap(a,b);
    if(b==0)return a;
    else return gcd(b,a%b);
}

struct Point{
    int x,y;
};

int ans=0;
int h,w,C;
vector<vector<int>> looked(h,vector<int>(w,-1));

int count(vector<vector<int>>& v,int c){
    Point init=Point{0,0};
    int target_color=v[0][0];
    if(target_color!=C){
        return -1;
    }
    queue<Point> q;
    q.push(init);
    int dx[4]={0,0,1,-1},dy[4]={1,-1,0,0};
    looked.clear();
    looked.resize(h,vector<int>(w,-1));
    looked[0][0]=1;
    int ret=1;
    while(!q.empty()){
        Point now=q.front();
        q.pop();
        rep(i,0,4){
            int nx=now.x+dx[i],ny=now.y+dy[i];
            if(0<=ny&&0<=nx&&ny<h&&nx<w&&looked[ny][nx]==-1){
                looked[ny][nx]=1;
                if(v[ny][nx]==target_color){
                    ret++;
                    q.push(Point{nx,ny});
                }
            }
        }
    }
    return ret;
}

void dfs(int deep,vector<vector<int>> v,int c){ //再起の回数、配列、どの色に変えるか
    if(deep==5){
        int ret=count(v,c);
        if(ans<ret){
            ans=ret;
            //printvv(v);
        }
        return;
    }
    int lu_color=v[0][0];
    if(lu_color==c){
        return ;
    }
    v[0][0]=c;
    Point init=Point{0,0};
    queue<Point> q;
    q.push(init);
    int dx[4]={0,0,1,-1},dy[4]={1,-1,0,0};
    looked.clear();
    looked.resize(h,vector<int>(w,-1));
    //vector<Point> changed;
    while(!q.empty()){
        Point now=q.front();
        q.pop();
        rep(i,0,4){
            int nx=now.x+dx[i],ny=now.y+dy[i];
            if(0<=ny&&0<=nx&&ny<h&&nx<w&&looked[ny][nx]==-1){
                looked[ny][nx]=1;
                if(v[ny][nx]==lu_color){
                    v[ny][nx]=c;
                    q.push(Point{nx,ny});
                    //changed.push_back(Point{nx,ny});
                }
            }
        }
    }
    rep(next_c,1,6+1){
        dfs(deep+1, v, next_c);
    }
    // rep(i,0,changed.size()){
    //     v[changed[i].y][changed[i].x]=lu_color;
    // }
    
    return;
    
}

signed main (){
    while(cin>>h>>w>>C){
        if(h+w+C==0)break;
        ans=0;
        vector<vector<int>> v(h,vector<int>(w));
        rep(i,0,h)rep(j,0,w)cin>>v[i][j];
        
        rep(init_c, 1, 6+1){
            dfs(0, v, init_c);
        }
        cout<<ans<<endl;
    }

}
/*
3 5 5
1 6 3 2 5
2 5 4 6 1
1 2 4 1 5
4 5 6
1 5 6 1 2
1 4 6 3 2
1 5 2 3 2
1 1 2 3 2
1 1 5
1
1 8 6
1 2 3 4 5 1 2 3
8 1 1
1
2
3
4
5
1
2
3
8 8 6
5 2 5 2 6 5 4 2
4 2 2 2 5 2 2 2
4 4 4 2 5 2 2 2
6 4 5 2 2 2 6 6
6 6 5 5 2 2 6 6
6 2 5 4 2 2 6 6
2 4 4 4 6 2 2 6
2 2 2 5 5 2 2 2
8 8 2
3 3 5 4 1 6 2 3
2 3 6 4 3 6 2 2
4 1 6 6 6 4 4 4
2 5 3 6 3 6 3 5
3 1 3 4 1 5 6 3
1 6 6 3 5 1 5 3
2 4 2 2 2 6 5 3
4 1 3 6 1 5 5 4
0 0 0
*/


Measured memory_bytes: 3120