#include<cstdio>
#include<algorithm>
#include<cmath>
using namespace std;
int t,n;
double l,w;
struct node{
    double l,r;
}a[15005];
bool operator <(const node &x,const node &y){
    if(x.l==y.l)return x.r>y.r;
    return x.l<y.l;
}
int main(){
    freopen("sprinkler.in","r",stdin);
    freopen("sprinkler.out","w",stdout);
    scanf("%d",&t);
    while(t--){
        scanf("%d%lf%lf",&n,&l,&w);
        bool can=1;
        w/=2.0;
        for(int i=1;i<=n;i++){
            double x,r;
            scanf("%lf%lf",&x,&r);
            if(r*r-w*w<0)can=0;
            if(can){
                double dis=sqrt(r*r-w*w);
                a[i].l=x-dis;
                a[i].r=x+dis;
            }
        }
        if(!can){
            printf("-1\n");
            continue;
        }
        sort(a+1,a+n+1);
        double now=0,nxt=0;
        int ans=1;
        for(int i=1;i<=n;i++){
            if(a[i].l<=now){
                nxt=max(nxt,a[i].r);
            }
            else{
                ans++;
                now=nxt;
                if(a[i].l>now)can=0;
                else nxt=max(nxt,a[i].r);
            }
        }
        if(!can||nxt<l){
            printf("-1\n");
        }
        else{
            printf("%d\n",ans);
        }
    }
    return 0;
}