#include <bits/stdc++.h>
using namespace std;
const int INF = 0x3f3f3f3f;
int a[500000 + 10];
map<int, vector<int> > each;
int sum[500000 + 10];
int totc = 0;
map<int, int> res;
int main() {
  int n, c;
  scanf("%d %d", &n, &c);
  for (int i = 1; i <= n; ++i) scanf("%d", &a[i]);
  for (int i = 1; i <= n; ++i) {
    sum[i] = sum[i - 1] + (a[i] == c);
    totc += (a[i] == c);
    if (a[i] != c) {
      each[a[i]].push_back(i);
    }
  }
  map<int, vector<int> >::iterator ite;
  int rec = 0;
  for (ite = each.begin(); ite != each.end(); ite++) {
    vector<int> tmp = ite->second;
    int SZ = (tmp).size();
    int tmp_rec = 0;
    if (SZ) tmp_rec = 1;
    rec = max(rec, tmp_rec);
    for (int i = 1; i <= SZ - 1; ++i) {
      tmp_rec++;
      tmp_rec -= (sum[tmp[i]] - sum[tmp[i - 1]]);
      tmp_rec = max(tmp_rec, 1);
      rec = max(rec, tmp_rec);
    }
  }
  printf("%d\n", totc + rec);
  return 0;
}
