圆---已经两点及其半径求圆心

　　UVALive - 6477

/*  gyt
       Live up to every day            */
#include<cstdio>
#include<cmath>
#include<iostream>
#include<algorithm>
#include<vector>
#include<stack>
#include<cstring>
#include<queue>
#include<set>
#include<string>
#include<map>
#include <time.h>
#define PI acos(-1)
using namespace std;
typedef long long ll;
typedef double db;
const int maxn = 30+10;
const ll maxm = 1e7;
const int modd = 10000007;
const int INF = 1<<30;
const db eps = 1e-8;
struct point {
    double x, y;
}p[maxn], a1, a2;
db r;
int n;

int sgn(db x) {
    return x<-eps?-1:x<eps?0:1;
}
double dis(point a,point b)    {
    return (a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y);
}
void look_center(point a,point b)  {
    point aa,bb,mid;
    aa.x = b.x-a.x;
    aa.y = b.y-a.y;
    mid.x = (a.x+b.x)/2.0;
    mid.y = (a.y+b.y)/2.0;
    double dist = dis(a,mid);
    double c = sqrt(r*r-dist);
    if (a.y==b.y) {
        a1.x=mid.x;  a1.y=mid.y+c;
        a2.x=mid.x;  a2.y=mid.y-c;
        return;
    }
    double ang = atan(-aa.x/aa.y);
    a1.x = mid.x + c*cos(ang);
    a1.y = mid.y + c*sin(ang);
    a2.x = mid.x - c*cos(ang);
    a2.y = mid.y - c*sin(ang);
}
void solve() {
    scanf("%lf%d", &r, &n);
    for (int i=0; i<n; i++) {
        scanf("%lf%lf", &p[i].x, &p[i].y);
    }
    int ans=1;
    if (n<=1)  printf("%d
", n);
    else {
        for (int i=0; i<n; i++) {
            for (int j=i+1; j<n; j++) {
                if (dis(p[i], p[j])>4.0*r*r)  continue;
                 look_center(p[i], p[j]);
                int num=0;
                for (int k=0; k<n; k++) {
                    if (sgn(dis(a1, p[k])-r*r)<=0)  num++;
                }
                ans=max(ans, num);
                num=0;
                for (int k=0; k<n; k++) {
                    if (sgn(dis(a2, p[k])-r*r)<=0)  num++;
                }
                ans=max(ans, num);
            }
        }
        cout<<ans<<endl;
    }
}

int main() {
    int t = 1;
    //freopen("in.txt","r",stdin);
  //  freopen("gcd.out","w",stdout);
    scanf("%d", &t);
    while(t--)
        solve();
    return 0;
}