#include <bits/stdc++.h>
using namespace std;
const int N = 15000 + 10;
struct node{
    int l, r;
};
bool cmp(node a, node b){
    return a.r < b.r;
}
int t;
int n, L, W, s, e, ans;
node a[N];
int main(){
    cin >> t;
    while(t--){
        s = 114514;ans = 0;
        cin >> n >> W >> L;
        for(int i = 1;i <= 15000;i++) a[i].l = a[i].r = 0;
        for(int i = 1;i <= n;i++){ 
            int d, r;
            cin >> d >> r;
            if(r >= L / 2 && d <= W){
               a[i].l = d - r, a[i].r = d + r; 
               s = min(a[i].l, s); 
            }
        }
        sort(a + 1, a + n + 1, cmp);
        e = a[1].r;
        for(int i = 2;i <= n;i++){
            if(e > a[i].l){
                ans++;
                e = a[i].r;
            }
        }
        if(s < 0 && e > W){
            cout<<ans<<endl;
        }
        else{
            cout<<-1<<endl;
        }
    }
}