#include <bits/stdc++.h>
using namespace std;
const double pi = acos(-1), eps = 1e-9;
double norm(double a) {
  while (a >= pi) a -= 2 * pi;
  while (a < -pi) a += 2 * pi;
  return a;
}
pair<double, double> tangent(double r, double ata, double len) {
  double cs = r / len;
  if (cs < -1) cs = -1;
  if (cs > 1) cs = 1;
  double ang = acos(cs);
  return make_pair(norm(ata - ang), norm(ata + ang));
}
long long int C(int a) { return a * 1ll * (a - 1) / 2; }
int x[100500], y[100500];
double ang[100500], len[100500];
int t[800500];
void build(int v, int tl, int tr) {
  if (tl == tr)
    t[v] = 0;
  else {
    int tm = (tl + tr) / 2;
    build(v * 2, tl, tm);
    build(v * 2 + 1, tm + 1, tr);
    t[v] = t[v * 2] + t[v * 2 + 1];
  }
}
int sum(int v, int tl, int tr, int l, int r) {
  if (l > r) return 0;
  if (l == tl && r == tr) return t[v];
  int tm = (tl + tr) / 2;
  return sum(v * 2, tl, tm, l, min(r, tm)) +
         sum(v * 2 + 1, tm + 1, tr, max(l, tm + 1), r);
}
void update(int v, int tl, int tr, int pos, int new_val) {
  if (tl == tr)
    t[v] += new_val;
  else {
    int tm = (tl + tr) / 2;
    if (pos <= tm)
      update(v * 2, tl, tm, pos, new_val);
    else
      update(v * 2 + 1, tm + 1, tr, pos, new_val);
    t[v] = t[v * 2] + t[v * 2 + 1];
  }
}
long long int solve(vector<pair<double, double> > &v) {
  if (v.empty()) return 0;
  int n = v.size();
  long long int ans = 0;
  int now = 0;
  for (auto &p : v) {
    if (p.first > p.second) swap(p.first, p.second);
  }
  sort(v.begin(), v.end());
  build(1, 0, 2 * n - 1);
  vector<double> cmp;
  for (auto &p : v) cmp.push_back(p.first), cmp.push_back(p.second);
  sort(cmp.begin(), cmp.end());
  for (auto &p : v) {
    p.first = lower_bound(cmp.begin(), cmp.end(), p.first) - cmp.begin();
    p.second = lower_bound(cmp.begin(), cmp.end(), p.second) - cmp.begin();
  }
  for (auto &p : v) {
    if (p.first > p.second) swap(p.first, p.second);
    int l = p.first;
    int r = p.second;
    update(1, 0, 2 * n - 1, r, 1);
    ans += sum(1, 0, 2 * n - 1, r + 1, 2 * n - 1);
  }
  build(1, 0, 2 * n - 1);
  for (auto &p : v) {
    update(1, 0, 2 * n - 1, p.first, 1);
  }
  for (auto &p : v) {
    ans += sum(1, 0, 2 * n - 1, p.second + 1, 2 * n - 1);
  }
  return ans;
}
int main() {
  ios_base::sync_with_stdio(false);
  int n;
  cin >> n;
  long long int k;
  cin >> k;
  for (int i = 0; i < n; i++) {
    cin >> x[i] >> y[i];
    if (x[i] == 0 && y[i] == 0) {
    } else {
      ang[i] = atan2(y[i], x[i]);
    }
    len[i] = hypot(y[i], x[i]);
  }
  double L = 0, R = 1e5;
  for (int t = 0; t < 60; t++) {
    double m = (L + R) / 2;
    long long int inc = 0;
    vector<pair<double, double> > v;
    for (int i = 0; i < n; i++) {
      if (len[i] > m + eps) {
        auto p = tangent(m, ang[i], len[i]);
        v.push_back(p);
      } else {
        ++inc;
      }
    }
    long long int a = C(n) - C(n - inc);
    long long int b = solve(v);
    long long int kol = a + b;
    if (kol >= k)
      R = m;
    else
      L = m;
  }
  printf("%.10f", R);
  return 0;
}
