#include<bits/stdc++.h>
#define int long long
using namespace std;
const int maxn=4e5+10;
int T,n,A,B,a[maxn]; 
signed main(){
	scanf("%lld",&T);
	while(T--){
		scanf("%lld%lld%lld",&n,&A,&B);
		for(int i=1;i<=2*n;i++)
			scanf("%lld",&a[i]);
		sort(a+1,a+1+2*n);
		int ans=0,flag=0,ans2=0,flag2=(a[2*n]-a[1]>A);
		for(int i=2;i<=2*n;i+=2){
			if(a[i]-a[i-1]>A){
				flag=1;
				break;
			}
			ans+=(a[i]-a[i-1]<=B);
		}
		for(int i=3;i<2*n;i+=2){
			if(a[i]-a[i-1]>A){
				flag2=1;
				break;
			}
			ans2+=(a[i]-a[i-1]<=B);
		}
		if(flag&&flag2) puts("-1");
		else printf("%lld\n",max(ans,ans2));
	}
	return 0;
}