#include <bits/stdc++.h>
using namespace std;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int ms = 512345;
int arr[ms];
vector<int> pos[ms];
int sum_c[ms];
int get_qtd(int l, int r) {
  if (!l) return sum_c[r];
  return sum_c[r] - sum_c[l - 1];
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  int n, c;
  cin >> n >> c;
  for (int i = 0; i < n; ++i) {
    cin >> arr[i];
    pos[arr[i]].push_back(i);
    sum_c[i] = arr[i] == c;
    if (i) sum_c[i] += sum_c[i - 1];
  }
  int ans = 0;
  for (int i = 1; i < ms; ++i) {
    if (i == c || pos[i].empty()) continue;
    int now = 1, maxi = 1;
    for (int j = 1; j < (int)pos[i].size(); ++j) {
      now = max(1, now + 1 - get_qtd(pos[i][j - 1], pos[i][j]));
      maxi = max(now, maxi);
    }
    ans = max(ans, maxi);
  }
  cout << get_qtd(0, n - 1) + ans << '\n';
  return 0;
}
