#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1e9 + 7;
const int INF = 0x3f3f3f3f;
const long long LINF = 0x3f3f3f3f3f3f3f;
int n, c;
vector<int> loc[500100];
int arr[500100];
int csum[500100];
int main() {
  int i, t = 0;
  scanf("%d%d", &n, &c);
  for (i = 0; i < n; i++) {
    scanf("%d", &arr[i]);
    if (arr[i] == c) {
      csum[i] = 1;
      t++;
    } else
      loc[arr[i]].push_back(i);
  }
  for (i = 1; i < n; i++) csum[i] += csum[i - 1];
  int j;
  int ans = t;
  for (i = 1; i <= 500001; i++) {
    if (loc[i].empty()) continue;
    vector<int> vec;
    for (j = 0; j < loc[i].size(); j++) vec.push_back(csum[loc[i][j]]);
    int mini = 1e9;
    for (j = 0; j < vec.size(); j++) {
      mini = min(mini, j - vec[j]);
      ans = max(ans, t + j - vec[j] - mini + 1);
    }
  }
  printf("%d\n", ans);
  return 0;
}
