#include <iostream>
#include <vector>
#include <set>
#include <algorithm>

#ifndef LOCAL
	#define cerr if(false)cerr
#endif

using namespace std;
using ll = long long;

const int N = 1e6 + 123;

void debug(vector<int>&a, string end="\n") {
	for (int x : a) {
		cerr << x << " ";
	}
	cerr << end;
}

int n, A, B, a[N];

int dist(int i, int j) {
	return abs(a[i] - a[j]);
}

void solve() {
	cin >> n >> A >> B;
	for (int i = 0 ; i < 2 * n ; ++ i) {
		cin >> a[i];
	}
	sort(a, a + 2 * n);
	for (int i = 1 ; i < 2 * n ; i += 2) {
		if (a[i] - a[i - 1] > A) {
			cout << -1;
			return;
		}
	}
	int k = -1;
	int ans = 0;
	for (int i = 0 ; i < n * 2 ; ++ i) {
		if (dist(i, i + 1) <= B && (k == -1 || (i + 2 < n * 2 && dist(k, i + 2) <= A))) {
			ans++;
			i++;
			continue;
		}
		if (k == -1) {
			k = i;
		} else {
			k = -1;
		}
	}
	cout << ans;
}

int main() {
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	int t;
	cin >> t;
	while (t--) {
		solve();
		cout << "\n";
	}
}