#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, c = 0;
  long long d;
  cin >> n >> d;
  int a[n];
  for (int i = 0; i < n; i++) cin >> a[i];
  sort(a, a + n);
  for (int i = 0; i < n - 1; i++) {
    for (int j = i + 1; j < n; j++) {
      if (a[j] - a[i] > d) {
        break;
      } else
        c = c + 2;
    }
  }
  cout << c;
}
