#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
const int maxn = 1e5 + 10;
constexpr double eps = 1e-8;
const double pi = acos(-1.0);
struct Point {
  double x, y, dis, ang;
  Point(double x = 0, double y = 0) : x(x), y(y) {
    dis = sqrt(x * x + y * y);
    ang = atan2(y, x);
  }
  bool operator<(const Point& b) { return x < b.x || (x == b.x && y < b.y); }
  void print() { cout << x << ' ' << y << ' ' << dis << ' ' << ang << '\n'; }
};
Point operator+(Point A, Point B) { return Point(A.x + B.x, A.y + B.y); }
Point operator-(Point A, Point B) { return Point(A.x - B.x, A.y - B.y); }
Point operator*(Point A, double B) { return Point(A.x * B, A.y * B); }
Point operator/(Point A, double B) { return Point(A.x / B, A.y / B); }
class BIT {
 private:
  int n;
  vector<int> bit;

 public:
  int lowbit(int x) { return x & -x; }
  void modify(int i, int x) {
    for (; i <= n; i += lowbit(i)) bit[i] += x;
  }
  int query(int i) {
    int ans = 0;
    for (; i; i -= lowbit(i)) ans += bit[i];
    return ans;
  }
  int qend(int i) { return query(n) - query(i - 1); }
  int qrange(int l, int r) {
    if (r < l) return 0;
    return query(r) - query(l - 1);
  }
  BIT(int size) {
    this->n = size;
    bit = vector<int>(size + 10, 0);
  }
};
int n;
ll k;
Point a[maxn];
int main() {
  cin >> n >> k;
  for (int i = 0; i < n; i++) {
    double x, y;
    scanf("%lf%lf", &x, &y);
    a[i] = Point(x, y);
  }
  auto check = [&](double x) {
    int cnt = 0;
    vector<Point> p;
    for (int i = 0; i < n; i++) {
      if (a[i].dis <= x)
        cnt++;
      else
        p.push_back(a[i]);
    }
    int m = p.size();
    vector<pair<double, double>> tang(m);
    vector<double> c;
    for (int i = 0; i < m; i++) {
      double rot = abs(acos(x / p[i].dis));
      auto res = make_pair(p[i].ang - rot + pi, p[i].ang + rot + pi);
      if (res.first < 0) res.first += pi * 2;
      if (res.second > 2 * pi) res.second -= 2 * pi;
      if (res.first > res.second) res.second += 2 * pi;
      tang[i] = res;
      c.push_back(res.first);
      c.push_back(res.second);
    }
    sort(c.begin(), c.end());
    vector<pair<int, int>> t(m);
    for (int i = 0; i < m; i++) {
      t[i].first =
          lower_bound(c.begin(), c.end(), tang[i].first) - c.begin() + 1;
      t[i].second =
          lower_bound(c.begin(), c.end(), tang[i].second) - c.begin() + 1;
    }
    const int N = m + m;
    BIT b1(N + 10);
    sort(t.begin(), t.end());
    ll ans = 0;
    for (int i = 0; i < m; i++) {
      ans += b1.qrange(t[i].first, t[i].second);
      b1.modify(t[i].second, 1);
    }
    for (int i = 0; i < m; i++) {
      int idx = lower_bound(c.begin(), c.end(), tang[i].first + 2 * pi) -
                c.begin() + 1;
      int _idx = lower_bound(c.begin(), c.end(), tang[i].second + 2 * pi) -
                 c.begin() + 1;
      ans += b1.qrange(idx, _idx - 1);
    }
    return 1ll * n * (n - 1) / 2 - ans;
  };
  double l = 0, r = 2e4;
  while (r - l > eps) {
    double mid = (l + r) / 2;
    if (check(mid) < k)
      l = mid;
    else
      r = mid;
  }
  printf("%.10f\n", r);
}
