#include <string>
#include <vector>
#include <algorithm>
#include <map>
#include <set>
#include <stack>
#include <queue>
#include <math.h>
#include <iostream>
#include <fstream>
#include <stdio.h>
#include <stdlib.h>
#include <cassert>
#include <string.h>

#include <time.h>
#include <random>
#include <iomanip>
using namespace std;

#define ll long long
#define N 10005

pair<ll,ll> pts[N];

double getAngle(pair<ll,ll> a, pair<ll,ll> b, pair<ll,ll> c) {
    pair<ll,ll> v1, v2;
    
    v1 = {b.first-a.first, b.second-a.second};
    v2 = {b.first-c.first, b.second-c.second};
    
    ll dot = v1.first*v2.first + v1.second*v2.second;
    ll det = v1.first*v2.second - v1.second*v2.first;
    
    return atan2(det, dot);
}

void solve() {
    ll r, n;
    cin >> r >> n;
    double jagged = 0;
    double angle = 0;
    pair<ll,ll> pt;
    for (ll i = 0; i < n; i++) {
        cin >> pts[i].first >> pts[i].second;
    }
    
    for (ll i = 0; i < n; i++) {
        ll iP = (i-1)%n;
        ll iN = (i+1)%n;
        if (iP < 0)
            iP += n;
        jagged += sqrt(pow(pts[iP].first-pts[i].first, 2)+pow(pts[iP].second-pts[i].second,2));
        
        double ang = getAngle(pts[iP], pts[i], pts[iN]);
        if (ang < 0)
            ang += 2*M_PI;
        ang = abs(M_PI-ang);
        //cout << ang << endl;
        angle += ang;
    }
    
    double angleTotal = angle*r;
    
    if (angleTotal > jagged)
        cout << "Not possible" << endl;
    else {
        double factor = (jagged-angleTotal)/jagged;
        cout << factor << endl;
    }
}

int main() {
    std::ios::sync_with_stdio(false);
    cin.tie(0);
    ll t;
    cin >> t;
    for (ll i = 0; i < t; i++) {
        solve();
    }
}