#include <bits/stdc++.h>

using namespace std;
using ll = long long;

void solve() {
    int n;
    ll A,B;
    cin >> n >> A >> B;

    vector<ll> a(2*n);
    for (int i = 0; i < 2*n; i++) cin >> a[i];
    sort(a.begin(),a.end());

    // -1の判定
    for (int i = 0; i < 2*n; i+=2) {
        if (abs(a[i]-a[i+1]) > A) {
            cout << -1 << endl;
            return;
        }
    }

    vector<bool> used(2*n);
    int ans = 0;
    int tmp_pos = -1;
    for (int i = 0; i < 2*n; i++) {
        if (used[i]) continue;
        used[i] = true;
        if (tmp_pos != -1 && abs(a[i+2]-a[tmp_pos]) > A) {
            tmp_pos = -1;
        }
        else {
            if (abs(a[i+1]-a[i]) <= B) {
                ++ans;
                used[i+1] = true;
            }
            else {
                if (tmp_pos == -1) {
                    tmp_pos = i;
                }
                else {
                    tmp_pos = -1;
                }
            }
        }
    }

    cout << ans << endl;
}

int main(void) {
    int t;
    cin >> t;

    while (t--) {
        solve();
    }
    
    return 0;
}