#include <bits/stdc++.h>
using namespace std;
const int N = 5e5 + 10, lim = 5e5;
int firste[N], nexte[N], v[N];
int a[N], sum[N], cnt[N];
int n, c, e;
void build(int x, int y) {
  nexte[++e] = firste[x];
  firste[x] = e;
  v[e] = y;
}
int main() {
  int ans = 0;
  scanf("%d%d", &n, &c);
  for (int i = 1; i <= n; ++i) {
    scanf("%d", &a[i]);
    if (a[i] == c)
      cnt[i] = cnt[i - 1] + 1;
    else
      cnt[i] = cnt[i - 1];
  }
  ans = cnt[n];
  for (int i = n; i; --i) build(a[i], i);
  for (int i = 1; i <= lim; ++i)
    if (i != c && firste[i]) {
      int len = 0, last = 0;
      for (int p = firste[i]; p; p = nexte[p]) {
        if (last) {
          sum[++len] = -(cnt[v[p]] - cnt[last]);
          sum[len] += sum[len - 1];
        }
        last = v[p];
        sum[++len] = 1;
        sum[len] += sum[len - 1];
      }
      int tmp = 0, small = 0, tans = 0;
      for (int j = 1; j <= len; ++j) {
        tmp = sum[j];
        if (tmp < small) small = tmp;
        tans = max(tans, tmp - small);
      }
      ans = max(ans, tans + cnt[n]);
    }
  printf("%d\n", ans);
  return 0;
}
