#include<bits/stdc++.h>

using namespace std;
//定义大数组，放在主函数外边
int a[1000001], n, f, i, j, k;

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

    k = 0;
    //对数组进行一次排序
    sort(a + 1, a + (n + 1));
    //双重循环
    for (i = 1; i < n; i++)
        for (j = i + 1; j <= n; ++j) {
            if (a[j] - a[i] > f)
                break;
            k++;
        }
    cout << k << endl;
    return 0;
}