#include <bits/stdc++.h>
#define debug(x) cout << #x << " :==  " << x << endl
#define FINISH cout << "FINISH" << endl;
#define el '\n'
using namespace std;
using ll = long long;
const int inf = 1000000000;
void solve()
{
	int n;
	ll B, A;
	cin >> n >> A >> B;
	vector<ll> a(n * 2 + 1, 0);
	for (int i = 1; i <= n * 2; i++) {
		cin >> a[i];
	}
	sort(next(a.begin()), a.end());
	for (int i = 1; i <= n; i++) {
		if (a[i * 2] - a[i * 2 - 1] > A) {
			cout << "-1" << el;
			return;
		}
	}
	// FINISH
	vector<ll> dp(n + 1, 0);
	vector<ll> s(n + 1, 0);
	for (int i = 1; i < n; i++) {
		if (a[i * 2 + 1] - a[i * 2] <= B)
			s[i] = 1;
		if (a[i * 2 + 1] - a[i * 2] > A)
			s[i] = -inf;
		s[i] = s[i - 1] + s[i];
	}
	/*cout << "a:: ";
	for (int i = 1; i <= n * 2; i++) {
		cout << a[i] << " ";
	}
	cout << endl;
	cout << "s:: ";
	for (int i = 1; i < n; i++) {
		cout << s[i] << " ";
	}
	cout << endl;*/
	int l = 0;
	multiset<ll> st;
	st.insert(0);
	for (int i = 1; i <= n; i++) {
		int res = 0;
		if (a[i * 2] - a[i * 2 - 1] <= B)
			res = 1;
		if (a[i * 2] - a[i * 2 - 1] > A)
			res = -inf;
		dp[i] = dp[i - 1] + res;
		// cout << i << " " << dp[i] << endl;
		while (l < i && a[i] - a[l] > A) {
			st.erase(st.find(dp[l] - s[l]));
			l++;
		}
		// cout << i << " " << l << endl;
		dp[i] = max(dp[i], *st.rbegin() + s[i - 1]);
		if (i != n)
			st.insert(dp[i] - s[i]);
		/*debug(i);
		debug(dp[i]);*/
	}
	cout << dp[n] << el;
}
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	cout.tie(nullptr);
	int T = 1;
	cin >> T;
	while (T--) {
		solve();
	}
	return 0;
}