#include <bits/stdc++.h>
using namespace std;
const int N = 5e5 + 10;
const int INF = 0x3f3f3f3f;
int a[N], pre[N], suf[N], dp[N];
vector<int> G[N];
int main() {
  int n, c;
  scanf("%d%d", &n, &c);
  for (int i = 1; i <= n; i++) {
    scanf("%d", a + i);
    G[a[i]].push_back(i);
    pre[i] = pre[i - 1];
    if (a[i] == c) pre[i]++;
  }
  for (int i = n; i >= 1; i--) {
    suf[i] = suf[i + 1];
    if (a[i] == c) suf[i]++;
  }
  int ans = 0;
  for (int i = 1; i < N; i++) {
    for (int j = 0; j < G[i].size(); j++) {
      if (j == 0)
        dp[j] = pre[G[i][j] - 1] + 1;
      else
        dp[j] = max(dp[j - 1] + 1, pre[G[i][j] - 1] + 1);
      ans = max(ans, dp[j] + suf[G[i][j] + 1]);
    }
  }
  printf("%d\n", ans);
  return 0;
}
