#include <bits/stdc++.h>
using namespace std;
static const long long maxLL = (long long)1 << 62;
const long long MOD = 1000000007;
const long long INF = 1e18;
long long N, C, A[1000100], S[1000100];
vector<long long> V[1000100];
signed main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cin >> N >> C;
  for (long long i = 0; i < N; i++) {
    cin >> A[i];
    S[i + 1] = S[i] + (A[i] == C);
    if (A[i] != C) V[A[i]].push_back(i + 1);
  }
  long long ma = S[N];
  for (long long i = 1; i < 500050; i++)
    if (V[i].size()) {
      long long ok = 1, cur = 1, mi = 0;
      for (long long j = 1; j < V[i].size(); j++) {
        cur -= S[V[i][j]] - S[V[i][j - 1]];
        mi = min((mi), (cur));
        cur++;
        ok = max((ok), (cur - mi));
      }
      ma = max((ma), (S[N] + ok));
    }
  cout << ma << '\n';
  return 0;
}
