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]; veq[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; }