#include <bits/stdc++.h>
#include <unistd.h>

using namespace std;

#define DEBUG(x) cerr<<#x<<": "<<x<<endl;
#define DEBUG_VEC(v) cerr<<#v<<":";for(int i=0;i<v.size();i++) cerr<<" "<<v[i]; cerr<<endl
#define DEBUG_MAT(v) cerr<<#v<<endl;for(int i=0;i<v.size();i++){for(int j=0;j<v[i].size();j++) {cerr<<v[i][j]<<" ";}cerr<<endl;}


typedef long long ll;
#define vi vector<int>
#define vl vector<ll>
#define vii vector< vector<int> >
#define vll vector< vector<ll> >
#define vs vector<string>
#define pii pair<int,int>
#define pis pair<int,string>
#define psi pair<string,int>
#define pll pair<ll,ll>
template<class S, class T> pair<S, T> operator+(const pair<S, T> &s, const pair<S, T> &t) { return pair<S, T>(s.first + t.first, s.second + t.second); }
template<class S, class T> pair<S, T> operator-(const pair<S, T> &s, const pair<S, T> &t) { return pair<S, T>(s.first - t.first, s.second - t.second); }
template<class S, class T> ostream& operator<<(ostream& os, pair<S, T> p) { os << "(" << p.first << ", " << p.second << ")"; return os; }
#define X first
#define Y second
#define rep(i,n) for(int i=0;i<(n);i++)
#define rep1(i,n) for(int i=1;i<=(n);i++)
#define rrep(i,n) for(int i=(n)-1;i>=0;i--)
#define rrep1(i,n) for(int i=(n);i>0;i--)
#define REP(i,a,b) for(int i=a;i<b;i++)
#define in(x, a, b) (a <= x && x < b)
#define all(c) c.begin(),c.end()
template<class T> bool chmax(T &a, const T &b) { if (a<b) { a = b; return 1; } return 0; }
template<class T> bool chmin(T &a, const T &b) { if (a>b) { a = b; return 1; } return 0; }
#define UNIQUE(v) v.erase(std::unique(v.begin(), v.end()), v.end());
const ll inf = 1000000001;
const ll INF = (ll)1e18 + 1;
const ll MOD = 1000000007;
//const ll MOD = 998244353;
const double pi = 3.14159265358979323846;
#define Sp(p) cout<<setprecision(15)<< fixed<<p<<endl;
int dx[4] = { 1,0, -1,0 }, dy[4] = { 0,1,0,-1 };
int dx2[8] = { 1,1,0,-1,-1,-1,0,1 }, dy2[8] = { 0,1,1,1,0,-1,-1,-1 };
#define fio() cin.tie(0); ios::sync_with_stdio(false);
//#define mp make_pair

int h, w, c;

int dfs(vii a, int d) {
  int now = a[1][1];
  int res = 0;
  rep1 (nex, 6) {
    if (now == nex) continue;
    if (d == 5 && nex != c) continue;
    auto b = a;
    queue<pii> qu;
    qu.push(pii(1, 1));
    b[1][1] = nex;
    while (!qu.empty()) {
      int i0 = qu.front().first, j0 = qu.front().second;
      qu.pop();
      rep (k, 4) {
        int ni = i0 + dx[k], nj = j0 + dy[k];
        if (b[ni][nj] == now) {
          b[ni][nj] = nex;
          qu.push(pii(ni, nj));
        }
      }
    }

    if (nex == c) {
      vii used(h + 2, vi(w + 2));
      qu.push(pii(1, 1));
      int cnt = 1;
      used[1][1] = true;
      while (!qu.empty()) {
        int i0 = qu.front().first, j0 = qu.front().second;
        qu.pop();
        rep (k, 4) {
          int ni = i0 + dx[k], nj = j0 + dy[k];
          if (b[ni][nj] == nex && !used[ni][nj]) {
            cnt++;
            qu.push(pii(ni, nj));
            used[ni][nj] = true;
          }
        }
      }
      chmax(res, cnt);
    }
    
    if (d != 5) chmax(res, dfs(b, d + 1));
  }
  return res;
}

int main() {
  while (true) {
    cin >> h >> w >> c;
    if (w == 0 && h == 0) return 0;
    vii a(h + 2, vi(w + 2, -1));
    int si, sj;
    rep1 (i, h) {
      rep1 (j, w) {
        cin >> a[i][j];
      }
    }

    cout << dfs(a, 1) << endl;
  }
}



Measured memory_bytes: 3148