#include <bits/stdc++.h>
using namespace std;
const int N=1e6+7;
#define int long long 
int a[N],n,c,ans,cnt[N];
signed main(){
	freopen("Triplets.in","r",stdin);
	freopen("Triplets.out","w",stdout);
	cin>>n>>c;
	for(int i=1;i<=n;i++){
		cin>>a[i];
		cnt[a[i]]++;
	}
	for(int i=1;i<c;i++){
		if(cnt[i]==0) continue;
		ans+=cnt[i];
		for(int j=i;j<i+(c/2);j++){
			if(cnt[j]==0) continue;
			ans+=cnt[j];
			for(int k=i+(c/2)+1;k<j+(c/2);k++){
				ans+=cnt[k];
			}
		}
	}
	cout<<ans/3;
	
	return 0;
}