#include <bits/stdc++.h>
using namespace std;

using ll = long long;
#define int ll
#define pb push_back
#define all(v) (v).begin(), (v).end()

void dbg_out() { cerr << endl; }
template<typename H, typename... T>
void dbg_out(H h, T... t) { cerr << ' ' << h; dbg_out(t...); }
#define dbg(...) { cerr << #__VA_ARGS__ << ':'; dbg_out(__VA_ARGS__); }

void solve() {
	int n, A, B; cin >> n >> A >> B;
	vector<int> a(2*n);
	for(int &x: a) cin >> x;
	sort(all(a));

	for(int i=0;i+1<2*n;i++) if(a[i+1] - a[i] > A) {
		cout << -1 << '\n';
		return;
	}

	int ans = 0;
	int cur = 0;
	while(cur < 2 * n) {
		if(a[cur+1] - a[cur] <= B) {
			cur += 2;
			ans += 1;
			continue;
		}

		int ptr = cur + 1;
		while(ptr + 1 < 2 * n && a[ptr + 1] - a[ptr] <= B && a[ptr + 2] - a[cur] <= A ) {
			ptr += 2;
			ans += 1;
		}
		cur = ptr + 1;
	}
	cout << ans << '\n';
}

signed main() {
	ios::sync_with_stdio(false); cin.tie(0);
	int t; cin >> t;
	while(t--)
		solve();
}