#include<string>
#include<iostream>
#include<cmath>
#include<algorithm>
using namespace std;
long long int arr[200005];
int main()
{
	
	int m = 0, n = 0,num=0;
	cin >> m >> n;
	long long int counter = 0;
	for(int i =1;i<=m;i++)
	{
		cin>>num;
		arr[num]++;
	}
	if(n>0)
	{
		for (int i = 1; i <= m - n; i++)
		{
			if (arr[i] > 0 && arr[i + n] > 0)
				{
					counter +=arr[i]*arr[i+n];
				}
		}
	}
	if(n==0)
	{
		for(int i =1;i<=m-n;i++)
		if(arr[i]>0)counter+=arr[i]*(arr[i]-1)/2;
	}
	cout << counter;
}