#include <bits/stdc++.h>
using namespace std;
const long long mod = 1000000007;
const long long inf = 1e18 * 4;
const long double pai = acos(-1);
int n, c;
vector<int> v[500009];
int num[500009];
int solve(int id) {
  if (v[id].size() == 0 || id == c) return 0;
  int sum = 1, mx = 1;
  for (int i = 1; i < v[id].size(); i++) {
    int L = v[id][i - 1], R = v[id][i];
    sum++;
    int xxx = num[R];
    if (L) xxx -= num[L - 1];
    sum -= xxx;
    if (sum <= 0) {
      sum = 1;
      continue;
    }
    mx = max(mx, sum);
  }
  return num[n - 1] + mx;
}
int main() {
  cin >> n >> c;
  for (int i = 0; i < n; i++) {
    int x;
    cin >> x;
    v[x].push_back(i);
    num[i] = (x == c);
  }
  for (int i = 1; i < n; i++) num[i] += num[i - 1];
  int mx = num[n - 1];
  for (int i = 1; i <= 500000; i++) {
    mx = max(mx, solve(i));
  }
  cout << mx << endl;
}
