#include <bits/stdc++.h>
using namespace std;

using ll = long long;
#define int ll
#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
using pii = pair<int, int>;
using vi = vector<int>;
#define fi first
#define se second
#define pb push_back

const int N=4e5+100;

int a[N];

signed main() {
    cin.tie(0)->sync_with_stdio(0);
    cin.exceptions(cin.failbit);

    int t;
    cin>>t;
    while(t--)
    {
        int n,A,B;
        cin>>n>>A>>B;
        n*=2;
        for(int i=1;i<=n;i++)
            cin>>a[i];
        sort(a+1,a+n+1);
        int ans=0;
        for(int l=1;l<=n;l++)
        {
            if(a[l+1]-a[l]>A)
            {
                ans=-1;
                break;
            }
            if(a[l+1]-a[l]<=B)
            {
                ans++;
                l+=2;
                continue;
            }
            int r=l+1;
            while(r+2<=n&&a[r+1]-a[r]<=B&&a[r+2]-a[l]<=A)
                r+=2,
                ans++;
            l=r+1;
        }
        cout<<ans<<"\n";
    }
}