#include <bits/stdc++.h>
using namespace std;
int n, c;
int a[500005];
int z[500005];
vector<pair<int, int> > v[500005];
int dp[500005];
int getroot(int vp, int ni) {
  if (v[vp][ni].second == -1) {
    int myans = z[v[vp][ni].first] + v[vp].size() - ni;
    int bestN = getroot(vp, ni - 1);
    int tans = z[v[vp][bestN].first] + v[vp].size() - bestN;
    if (myans >= tans) {
      v[vp][ni].second = ni;
    } else {
      v[vp][ni].second = bestN;
    }
  }
  return v[vp][ni].second;
}
int CheckA(int i) {
  int ni = v[a[i]].size() - (dp[i] - z[i]) - 1;
  v[a[i]][ni].second = getroot(a[i], ni);
  int temp = v[a[i]][ni].second;
  if (z[v[a[i]][temp].first] + v[a[i]].size() - temp > dp[i]) {
    return 1;
  } else {
    return 0;
  }
}
int main() {
  cin >> n >> c;
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  if (a[0] == c) {
    z[0] = 1;
  }
  for (int i = 1; i < n; i++) {
    z[i] = z[i - 1];
    if (a[i] == c) {
      z[i]++;
    }
  }
  v[a[0]].push_back(pair<int, int>(0, 0));
  dp[0] = 1;
  for (int i = 1; i < n; i++) {
    dp[i] = dp[i - 1];
    if (a[i] == c) {
      dp[i]++;
      continue;
    }
    v[a[i]].push_back(pair<int, int>(i, -1));
    if (v[a[i]].size() == 1) {
      v[a[i]][0].second = 0;
    }
    if (v[a[i]].size() + z[i] > dp[i]) {
      dp[i] += CheckA(i);
    }
  }
  cout << dp[n - 1] << endl;
  return 0;
}
