#include<bits/stdc++.h>
using namespace std;
#ifdef DEBUG
#include "E:/OI/normal/templates/debug.h"
#else
#define dbg(...) (void)0
#define msg(...) (void)0
#endif
#define ll long long
#define endl '\n'
#define PB emplace_back
#define PPB pop_back
#define MP make_pair
#define ALL(Name) Name.begin(),Name.end()
#define PII pair<int,int>
#define VI vector<int>
#define GI greater<int>
#define fi first
#define se second

const int N=200005;
int n,l1[N<<1],l2[N<<1];
ll A,B,a[N<<1],f[N<<1];

int main()
{
	ios::sync_with_stdio(false),cin.tie(nullptr);
	int _;cin>>_;while(_--)
{
	cin>>n>>A>>B;
	for(int i=1;i<=n<<1;i++)cin>>a[i];
	sort(a+1,a+(n<<1)+1);
	int bad=0;
	for(int i=1,j=0;i<=n<<1;i++)
	{
		while(a[i]-a[j]>A)++j;
		l1[i]=j;
		if(j==i){cout<<-(bad=1)<<endl;break;}
		l2[i]=a[i]-a[i-1]>B?i+1:l2[i-2];
	}
	if(bad)continue;
	for(int i=2;i<=n<<1;i+=2)
	{
		int tmp=max(l1[i]|1,l2[i-1]-1);
		f[i]=f[tmp-1]+(i-tmp>>1);
		if(a[i]-a[i-1]<=B)f[i]=max(f[i],f[i-2]+1);
	}
	cout<<f[n<<1]<<endl;
}

	return 0;
}