//Author: Kevin
#include<bits/stdc++.h>
//#pragma GCC optimize("O2")
using namespace std;
#define ll long long
#define ull unsigned ll
#define pb emplace_back
#define mp make_pair
#define ALL(x) (x).begin(),(x).end()
#define rALL(x) (x).rbegin(),(x).rend()
#define srt(x) sort(ALL(x))
#define rev(x) reverse(ALL(x))
#define rsrt(x) sort(rALL(x))
#define sz(x) (int)(x.size())
#define inf 0x3f3f3f3f
#define pii pair<int,int>
#define lb(v,x) (int)(lower_bound(ALL(v),x)-v.begin())
#define ub(v,x) (int)(upper_bound(ALL(v),x)-v.begin())
#define uni(v) v.resize(unique(ALL(v))-v.begin())
#define longer __int128_t
void die(string S){puts(S.c_str());exit(0);}
int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	int t;
	cin>>t;
	while(t--)
	{
		int n;
		ll a,b;
		cin>>n>>a>>b;
		vector<ll> vec(n+n);
		for(auto &x:vec) cin>>x;
		srt(vec);
		bool ok=1;
		for(int i=0;i<n+n;i+=2)
			if(vec[i+1]-vec[i]>a)
				ok=0;
		if(!ok)
		{
			cout<<"-1\n";
			continue;
		}
		int ans=0;
		ll lst=-1;
		for(int i=0;i<n+n;i+=2)
		{
			if(vec[i+1]-vec[i]<=b&&lst==-1)
			{
				if(~lst) ans++;
				lst=-1;
			}
			else
			{
				if(lst+vec[i+1]-vec[i]>a)
				{
					ans++;
					lst=-1;
				}
				lst+=vec[i+1]-vec[i];
			}
			if(~lst&&i<n+n-2&&vec[i+2]-vec[i+1]>b)
			{
				ans++;
				lst=-1;
			}
		}
		if(~lst) ans++;
		cout<<n-ans<<'\n';
	}
	return 0;
}