#include <iostream>
#include <queue>
#include <cmath>
#include <iomanip>
#include <fstream>
using namespace std;

struct element
{
    double X;
    int tip;
};

struct tochka
{
    double X;
    double Y;
};

void merge(element* a, int left, int mid, int right)
{
    int i, it = 0;
    int it_two = 0;
    element result[right - left];

    while (left + it < mid and mid + it_two < right)
    {
        if (a[left + it].X < a[mid + it_two].X)
        {
            result[it + it_two] = a[left + it];
            ++it;
        }
        else
        {
            result[it + it_two] = a[mid + it_two];
            ++it_two;
        }
    }
    while (left + it < mid)
    {
        result[it + it_two] = a[left + it];
        ++it;
    }
    while (mid + it_two < right)
    {
        result[it + it_two] = a[mid + it_two];
        ++it_two;
    }

    for (i = 0; i < it + it_two; ++i)
        a[left + i] = result[i];
}

void mergeSort_struct(element* a, int n)
{
    int i, j;
    for (i = 1; i < n; i *= 2)
        for (j = 0; j < n - i; j += 2 * i)
            merge(a, j, j + i, std::min(j + 2 * i, n));
}

int Func(double r, int n, tochka* A)
{
    element E[2 * n];
    double epsilon = 1e-6;
    int i, deg = 0, len = 0;
    for (i = 0; i < n; ++i)
    {
        if (abs(A[i].Y) < r)
        {
            E[2 * i].X = A[i].X - sqrt(r * r - (A[i].Y) * (A[i].Y)) - epsilon * (i + 1);
            E[2 * i].tip = 1;
            E[2 * i + 1].X = A[i].X + sqrt(r * r - (A[i].Y) * (A[i].Y)) + epsilon * (i + 1);
            E[2 * i + 1].tip = 0;
        }
        else
        {
            E[2 * i].X = 0;
            E[2 * i].tip = 2;
            E[2 * i + 1].X = 0;
            E[2 * i + 1].tip = 2;
        }
    }
    mergeSort_struct(E, 2 * n);
    for (i = 0; i < 2 * n; ++i)
    {
        if (deg < 0)
            deg = 0;
        if (E[i].tip == 1)
        {
            deg++;
            if (deg > len)
                len = deg;
        }
        if (E[i].tip == 0)
            deg--;
    }
    return len;
}

double binary_search (tochka* A, int n, int k) {

    double L = 0,M;
    double eps = 1e-4;
    double max_y = 0.0;
    for (int i = 0; i < n; ++i)
    {
        if (abs(A[i].Y) > max_y)
        max_y = abs(A[i].Y);
    }
    double R = max_y + 1.0;

    while (R - L > eps)
    {
        M = (R + L) / 2;
        if (Func(M, n, A) < k)
            L = M;
        else
            R = M;
    }
    return R;
}

int main()
{
    int n, k;
    tochka A[n];
    double res;

    int count_tests;

    ifstream ifs("123.txt");
    ifs >> count_tests;

    ofstream out("results.txt");
    for (int i = 0; i < count_tests; ++i)
    {

        ifs >> n;
        ifs >> k;
        tochka A[n] = {};

        for (int i = 0; i < n; ++i)
        {
            ifs >> A[i].X;
            ifs >> A[i].Y;
            cout << A[i].X << " " << A[i].Y << " \n";
        }


        res = binary_search(A, n, k);
        std::cout << std::setprecision(7) << res;
        out << std::setprecision(7) << res;
        out << '\n';

    }

    return 0;
}