#include <bits/stdc++.h>
using namespace std;
int n, x, ans;
int l[100005];
int main()
{
	cin >> n >> x;
	cin >> l[1];
	for(int i = 2, t = 2; t <= n; i++, t++)
	{
		cin >> l[i];
		if((l[i] == l[i-1] || l[i] + l[i-1] == x) && i != 1)
		{
			l[i] = l[i-1] = 0;
			i -= 2;
			ans++;
		}
	}
	n -= ans * 2;
	for(int i = 1, j = n; i < j; i++, j--)
	{
		if(l[i] == l[j] || l[i] + l[j] == x)
		{
			l[i] = l[j] = 0;
			ans++;
		}
		else break;
	}
	cout << ans;
    return 0;
}