#include <bits/stdc++.h>
using namespace std;
long long gcd1(long long a, long long b) {
  if (a == 0) return b;
  return gcd1(b % a, a);
}
long long modx(long long base, long long ex) {
  long long ans = 1LL, val = base;
  while (ex > 0LL) {
    if (ex & 1LL) ans = (ans * val) % 998244353LL;
    val = (val * val) % 998244353LL;
    ex = ex >> 1LL;
  }
  return ans;
}
const int maxn = 5e5 + 10;
int a[maxn], n, c;
int pre[maxn], suff[maxn];
int cnt[maxn], ans;
vector<int> v[maxn];
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> n >> c;
  for (int i = 1; i <= n; i++) {
    cin >> a[i];
    v[a[i]].push_back(i);
    if (a[i] == c)
      cnt[i] = cnt[i - 1] + 1;
    else
      cnt[i] = cnt[i - 1];
  }
  ans = cnt[n];
  for (int i = 1; i < maxn; i++) {
    if (i == c) continue;
    if (v[i].size() == 0) continue;
    for (int j = 0; j < v[i].size(); j++) {
      pre[j] = cnt[v[i][j]];
      pre[j]++;
      if (j > 0) pre[j] = max(pre[j], pre[j - 1] + 1);
    }
    for (int j = v[i].size() - 1; j >= 0; j--) {
      suff[j] = cnt[n] - cnt[v[i][j]];
      suff[j]++;
      if (j + 1 < v[i].size()) suff[j] = max(suff[j], suff[j + 1] + 1);
    }
    for (int j = 0; j < v[i].size(); j++) {
      ans = max(ans, pre[j] + suff[j] - 1);
    }
  }
  cout << ans << endl;
  return 0;
}
