#include <bits/stdc++.h>
using namespace std;
int destroy(list<int> row) {
  int totalDestroyed = 0, lastDestroyed = -1;
  int combo = 1;
  while (lastDestroyed != 0) {
    lastDestroyed = 0;
    combo = 1;
    list<int>::iterator it = row.begin();
    list<int>::iterator prev = it++;
    for (; it != row.end(); ++it) {
      if (*prev == *it) {
        combo++;
      } else {
        if (combo >= 3) {
          it = row.erase(prev, it);
          lastDestroyed += combo;
        }
        prev = it;
        combo = 1;
      }
    }
    totalDestroyed += lastDestroyed;
  }
  totalDestroyed += (combo >= 3 ? combo : 0);
  return totalDestroyed > 0 ? totalDestroyed - 1 : 0;
}
int main() {
  int N, K, X;
  cin >> N >> K >> X;
  list<int> row;
  int ball;
  for (int i = 0; i < N; ++i) {
    cin >> ball;
    row.push_back(ball);
  }
  int maxDestroyed = 0;
  for (list<int>::iterator it = row.begin(); it != row.end(); ++it) {
    it = row.insert(it, X);
    int destroyed = destroy(row);
    maxDestroyed = max(maxDestroyed, destroyed);
    it = row.erase(it);
  }
  cout << maxDestroyed;
}
