#include<bits/stdc++.h>
#define ll long long
#define pii pair<int,int>
#define lowbit(x) (x&-x)
#define log(x) (31^__builtin_clz(x))
using namespace std;
ll t[200005];
void solve(){
    int n;
    ll a,b;
    cin>>n>>a>>b;
    n<<=1;
    for(int i=1;i<=n;i++) cin>>t[i];
    sort(t+1,t+n+1);
    for(int i=1;i<=n;i+=2){
        if(t[i]+a<t[i+1]){
            cout<<"-1\n";
            return;
        }
    }
    int ans=t[2]-t[1]<=b,lastL=1;
    int lastans=ans;
    for(int i=3;i<=n;i+=2){
        // cout<<i<<" "<<lastL<<" "<<ans<<"\n";
        if(t[i+1]-t[lastL]>a||lastans){
            lastL=i;
            lastans=0;
            if(t[i+1]-t[i]<=b){
                ans++;
                lastL=i;
                lastans=1;
                continue;
            }
            continue;
        }
        if(t[i]-t[i-1]<=b){
            ans++;
            lastans=0;
            continue;
        }
        
        if(t[i+1]-t[i]<=b){
            ans++;
            lastans=1;
            lastL=i;
            continue;
        }
        lastans=0;
        lastL=i;
    }
    cout<<ans<<"\n";
}
int main(){
    ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    int t=1;
    cin>>t;
    while(t--)solve();
    return 0;
}
/*
4
1 2 1
42 69
2 3 1
1 2 3 4
2 5 1
6 1 3 4
1
5 19 1
1 7 8 9 10 11 12 13 14 20

*/