import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;

public class Main {
	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int n = Integer.parseInt(br.readLine());
		String[] sa = br.readLine().split(" ");
		int[] a = new int[n];
		Map<Integer, Integer> map = new HashMap<>();
		for (int i = 0; i < n; i++) {
			a[i] = Integer.parseInt(sa[i]);
			map.put(a[i], map.getOrDefault(a[i], 0) + 1);
		}
		br.close();

		Arrays.sort(a);
		long ans = 0;
		for (int k : map.keySet()) {
			int v = map.get(k);
			if (v >= 2) {
				int r = binarySearch(a, k * 2 - 1);
				int c1 = r + 1 - v;
				long c2 = (long) v * (v - 1) / 2;
				ans += c1 * c2;
			}
		}
		System.out.println(ans);
	}

	static int binarySearch(int[] array, int val) {
		int ng = array.length;
		int ok = -1;
		while (Math.abs(ok - ng) > 1) {
			int mid = (ok + ng) / 2;
			if (array[mid] <= val) {
				ok = mid;
			} else {
				ng = mid;
			}
		}
		return ok;
	}
}