#include<bits/stdc++.h>
using namespace std;
int main()
{
	ios_base::sync_with_stdio(false);
	int T;
	cin>>T;
	while(T--)
	{
		int n;
		long long A,B;
		cin>>n>>A>>B;
		n*=2;
		vector<long long> a(n+5);
		vector<int> R(n+5),f(n+5);
		for(int i=1;i<=n;i++)
			cin>>a[i];
		sort(a.begin()+1,a.begin()+n+1);
		int ok=1;
		for(int i=1;i<=n;i+=2)
			if(a[i+1]-a[i]>A)
				ok=0;
		if(not ok)
		{
			cout<<-1<<"\n";
			continue;
		}
		R[n+1]=n+1;R[n]=n;
		for(int i=n-1;i>=1;i--)
		{
			if(a[i+1]-a[i]<=B)
				R[i]=R[i+2];
			else
				R[i]=i;
		}
		int goA=1;
		for(int i=1;i<=n;i++)
		{
			while(goA<n and a[goA+1]-a[i]<=A)goA++;
			if(R[i]!=i)
				f[i+1]=max(f[i+1],f[i-1]+1);
			f[i+1]=max(f[i+1],f[i-1]);
			int t=min(R[i+1],goA);
			if(t%2==i%2)t--;
			f[t]=max(f[t],f[i]+(t-i)/2);
		}
		cout<<f[n]<<"\n";
	}
	
	return 0;
}