#include <bits/stdc++.h>
using namespace std;
int64_t mod = 1e9 + 7;
int64_t mod1 = 1e9 + 6;
int64_t power(int64_t a, int64_t b) {
  if (b == 0)
    return 1;
  else if (b % 2 == 0)
    return power((((a % mod) * (a % mod)) % mod), b / 2) % mod;
  else
    return ((a % mod) * (power((((a % mod) * (a % mod)) % mod), b / 2) % mod)) %
           mod;
}
std::vector<int64_t> g[500001];
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int64_t n, c;
  cin >> n >> c;
  int64_t cnt[n + 1], a[n + 1];
  cnt[0] = 0;
  for (int64_t i = 1; i <= 500000; i++) {
    g[i].push_back(0);
  }
  for (int64_t i = 1; i <= n; i++) {
    cin >> a[i];
    g[a[i]].push_back(i);
    cnt[i] = cnt[i - 1] + (a[i] == c);
  }
  int64_t ans = cnt[n];
  for (int64_t i = 1; i <= 500000; i++) {
    if (g[i].size() == 1) continue;
    int64_t mini = mod;
    for (int64_t j = 1; j < g[i].size(); j++) {
      mini = min(mini, j - 1 - cnt[g[i][j] - 1]);
      ans = max(ans, j - cnt[g[i][j]] - mini + cnt[n]);
    }
  }
  cout << ans << '\n';
}
