#include <iostream>
#include <string>
#include <cmath>
#include <set>
#include <map>
#include <algorithm>
#include <cstring>
#include <vector>
using namespace std;
typedef long long ll;
const int N =1e6 +5;
const int M = 1e9 +7;
const int inf = 0x3fffffff;
ll a[N];
ll quickpow(ll a,ll b){
	ll sum=1;
	while(b){
		if(b&1){
			sum=sum*a;
		}
		a=a*a;
		b>>=1;
	}
	return sum;
}
void solve(){
	ll n,k;
	cin>>n>>k;
	ll nn=quickpow(2,n);
	for(int i=1;i<=nn;i++){
		cin>>a[i];
	}
	sort(a+1,a+1+nn);
	ll l=1,r=nn;
	ll ss=0;
	while(l!=r){
		ll s=1;
		ll mid=(l+r)/2;
		for(ll i=mid+1;i<=r;i++){
			while(s<=mid&&a[i]-a[s]>k){
				s++;
			}
			if(s<=mid){
				ss++;
				s++;
			}
		}
		l=mid+1;
	}
	cout<<ss<<"\n";
}
int main() {
    ios::sync_with_stdio(0);cin.tie(0);
    //int t;cin>>t;while(t--)
    solve();
    return 0;
}