#include <bits/stdc++.h>
// #define pii pair<int, int>
#define int long long
// using namespace std;

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

    n <<= 1;
    std::vector<int> a(n);
    for (auto &i : a) std::cin >> i;
    std::sort(a.begin(), a.end());
    int l = 0, r = 1;
    int ans = 0;
    while (r < n) {
        if (a[r] - a[l] > A) {
            std::cout << "-1\n";
            return;
        }
        while (r + 2 < n && a[r + 2] - a[l] <= A) {
            r += 2;
        }
        std::stack<int> st;
        for (int i = l; i <= r; i++) {
            if (!st.empty() && a[i] - st.top() <= B) {
                st.pop();
                ans++;
            } else {
                st.push(a[i]);
            }
        }
        l = r + 1;
        r = l + 1;
    }
    std::cout << ans << '\n';
}

/*
4
1 2 1
42 69
2 3 1
1 2 3 4
2 5 1
6 1 3 4
5 19 1
1 7 8 9 10 11 12 13 14 20
*/

signed main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);

    int t = 1;
    std::cin >> t;
    for (int i = 0; i < t; ++i) {
        solve();
    }

    return 0;
}