#include<bits/stdc++.h>
#define int long long

using namespace std;
const int maxn = 4e5 + 5;
int n, x, y;
int a[maxn], pf[maxn], dp[maxn];

signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
//    freopen("test.inp", "r", stdin);
//    freopen("test.out", "w", stdout);
    int tst; cin >> tst; while (tst--)
    {
        cin >> n >> y >> x;
        n *= 2;
        for (int i = 1; i <= n; i++) cin >> a[i], dp[i] = 0, pf[i] = 0;
        sort(a + 1, a + n + 1);
        int fuck = 0;
        for (int i = 1; i <= n; i += 2)
            if (a[i + 1] - a[i] > y)
            {
                cout << "-1\n";
                fuck = 1;
                break;
            }
        if (fuck == 1) continue;
        for (int i = 2; i <= n; i++)
            pf[i] = pf[i - 2] + (a[i] - a[i - 1] <= x);
        queue<int> q;
        q.emplace(1);
        for (int i = 2; i <= n; i++)
        {
            for (; q.size() && a[i] - a[q.front()] > y; q.pop());
            if (q.size()) dp[i] = max(dp[i - 1], dp[q.front() - 1] + pf[i] - pf[q.front()]);
            while (q.size() && dp[q.front() - 1] - pf[q.front()] < dp[i - 1] - pf[i])
                q.pop();
            q.emplace(i);
        }
        cout << dp[n] << "\n";
    }
}