#include <iostream>
#include <algorithm>
#include <cstdlib>
#include <ctime>
#include <vector>
#include <set>
#include <string>
#include <map>
#include <queue>
#include <stack>
#include <cstring>
#include <cstdio>
#include <cmath>
#include <deque>
#define clr(a,b) memset(a,b,sizeof(a))
#define ll long long

using namespace std;

const int maxn=1e2+10;
int t,n;
double x,y,a[maxn];

int main()
{
	cin>>t;
	while(t--)
	{
		cin>>x>>y>>n;
		for(int i=0;i<n;i++)cin>>a[i];
		sort(a,a+n);
		
		int ans=0;
		double len=0;
		y/=2;
		for(int i=n-1;i>=0;i--)
		{
			if(a[i]>y)
			{
				ans++;
				len+=2*sqrt(1.0*(a[i]*a[i]-y*y));
				if(len>=x)
				{
					printf("%d\n",ans);
					break;
				}
			}
			else
			{
				printf("-1\n");
				break;
			}
		}
	}
}