#include <bits/stdc++.h>
#define ll long long
#define all(x) x.begin(),x.end()
#define answer(x) cout << (x ? "YES\n" : "NO\n")
#define test ios::sync_with_stdio(0); cin.tie(0); cout.tie(0); int T; cin >> T; while(T--)
#define go ios::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define F first
#define S second
using namespace std;

const int N = 200100;
ll n, d, a[N];

int main()
{
	ll ans = 0;

	cin >> n >> d;
	for(int i=1 ; i<=n;i ++) cin >> a[i];  


	for(int i=1 ;i<=n; i++) if(a[i] == d)
	{
		int j = i;
		ll l_ans = 0;
		while(i <= n && a[i] == d)
			l_ans ++, i ++;

		ans = max(ans, l_ans);
		i --;
	}

	if(d)
	{
		if(ans&1 && ans > 1) ans --; 
	}

	cout << ans;
}