#include <bits/stdc++.h>
 
#define fastio ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define ln '\n'
#define sep ' '
#define ve vector

using namespace std;
 
using pii = pair<int, int>;
using ll  = long long;
using ull = unsigned ll;
using ld  = long double;

constexpr int N=5e5+1;
int n,c,a[N],freq[N],freq2[N];
ve<int>q[N];

inline void solve()
{
  cin>>n>>c;
  for(int i=1;i<=n;++i)
  {
    cin>>a[i];
    freq2[i]=freq2[i-1];
    if(a[i]==c)++freq2[i];
  }

  int ans=freq2[n];

  for(int i=1;i<=n;++i)
  {
    int x=a[i];

    if(x==c)continue;

    freq[i]=(q[x].empty()?0:freq[q[x].back()])+1;

    q[x].push_back(i);

    while(!q[x].empty())
    {
      int j=q[x].front();
      int c1=freq[i]-freq[j]+1;
      int c2=freq2[i]-freq2[j-1];
      int c=c1-c2;

      ans=max(ans,freq2[n]+c);

      if(c>0)break;

      q[x].erase(q[x].begin(),q[x].begin()+1);
    }
  }

  cout<<ans<<ln;
}

int main()
{
  fastio;
  int t = 1; 
  //cin >> t;
  while (t--)
  {
    solve();
  }
  return 0;
}