#include <bits/stdc++.h>
#define rep1(i, l, r) for (int i = l; i <= int(r); ++i)
#define rep2(i, l, r) for (int i = l; i >= int(r); --i)
#define rer(i, l, r, a) rep1(i, l, r) read(a[i])
#define ptc putchar
#define il inline
using namespace std;
typedef long long ll;
const int MAXN = 4e5 + 10;
namespace stupid_lrc {
	template <typename T> il bool read(T &x) {
		x = 0; bool f = false; char ch;
		while (!isdigit(ch = getchar())) {
			f ^= !(ch ^ '-');
			if (ch == EOF) return false;
		}
		while (isdigit(ch)) x = (x << 1) + (x << 3) + (ch & 15), ch = getchar();
		if (f) x = ~x + 1; return true;
	}
	il int read() {int x; read(x); return x;}
	
	template <typename T> il void gmax(T &x, T y) {x = x > y ? x : y;}

	template <typename T, typename ...L>
	il bool read(T &x, L &...y) {return read(x) && read(y...);}
}
using namespace stupid_lrc;
int n, sum[MAXN], f[MAXN]; ll a[MAXN], A, B;

il void solve() {
	read(n, A, B); n <<= 1; rer(i, 1, n, a);
	sort(a + 1, a + 1 + n); ++A;
	for (int i = 1; i <= n; i += 2) if (a[i + 1] - a[i] > A) return puts("-1"), void();
	for (int i = 2; i <= n; ++i) sum[i] = sum[i - 2] + (a[i] - a[i - 1] <= B);
	deque <int> q; q.emplace_back(0);
	for (int i = 2; i <= n; i += 2) {
		while (q.size() && a[i] - a[q.front() + 1] > A) q.pop_front();
		if (q.size()) f[i] = f[q.front()] - sum[q.front() + 1] + sum[i - 1];
		gmax(f[i], f[i - 2] + (a[i] - a[i - 1] <= B));
		while (q.size() && f[q.back()] - sum[q.back() + 1] < f[i] - sum[i + 1]) q.pop_back();
		q.emplace_back(i);
	} printf("%d\n", f[n]);
}

int main() {
	for (int T = read(); T--; ) solve();
	return 0;
}