#include <bits/stdc++.h>

#define FOR(i, x, n) for(int i = x; i < n; i++)
#define F0R(i, n) FOR(i, 0, n)

#define F first
#define S second
#define PB push_back

#define WTF cout << "WTF" << endl;

#define IOS ios_base::sync_with_stdio(0); cin.tie(0);

using namespace std;

typedef long long LL;

typedef pair<int, int> PII;
typedef vector<int> VI;
typedef vector<PII> VPII;

const int N = 1e6 + 7;
const int INF = 1e9 + 7;

int n;
LL ns[N], dp[N];
LL a, b;

void solve() {
    cin >> n >> a >> b;
    n *= 2;
    F0R(i, n) cin >> ns[i];
    sort(ns, ns + n);
    fill(dp, dp + n + 1, 0);

    for(int i = 1; i < n; i += 2) {
        if (ns[i] - ns[i - 1] > a) {
            cout << -1 << endl;
            return;
        }
        if (ns[i] - ns[i - 1] <= b) dp[i] = max(dp[i], (i >= 2 ? dp[i - 2] + 1 : 1));
        if (i >= 2) dp[i] = max(dp[i - 2], dp[i]);
        if (i >= 3 && ns[i] - ns[i - 3] <= a && ns[i - 1] - ns[i - 2] <= b) 
            dp[i] = max(dp[i], (i >= 4 ? dp[i - 4] : 0) + 1);
    }

    cout << dp[n - 1] << endl;
}

int main() {
    IOS;
    int t; cin >> t;
    while(t--) solve();
}