#include <bits/stdc++.h>
using namespace std;
using LL = long long;
const double EPS = 1e-8;
const double PI = acos(-1.0);
const int MAXN = 100010;
struct Point {
  double x, y;
  double d;
};
double sqr(double a) { return a * a; }
int dcmp(double x) {
  if (x < -EPS)
    return -1;
  else
    return (x > EPS);
}
struct Interval {
  double l, r;
};
struct Stage {
  double l;
  int a;
  bool count;
};
class BIT {
 public:
  BIT(int _n) : n(_n) { x = vector<int>(n + 1, 0); }
  void add(int a, int b) {
    for (int i = a; i <= n; i += (i & -i)) x[i] += b;
  }
  int query(int a) {
    int ans = 0;
    for (int i = a; i > 0; i -= (i & -i)) ans += x[i];
    return ans;
  }
  int n;
  vector<int> x;
};
Interval get_interval(double r, Point p) {
  Interval x;
  double rad = atan2(p.y, p.x);
  if (dcmp(p.d - r) == 0) {
    x.l = x.r = rad;
    return x;
  }
  double diff = acos(r / p.d);
  x.l = rad - diff;
  x.r = rad + diff;
  if (x.l < -PI) {
    x.l += 2 * PI;
    x.r += 2 * PI;
  }
  return x;
}
Point p[MAXN];
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  LL k;
  cin >> n >> k;
  double l = 0, r = 0;
  for (int i = 0; i < n; ++i) {
    cin >> p[i].x >> p[i].y;
    p[i].d = sqrt(sqr(p[i].x) + sqr(p[i].y));
    r = max(r, p[i].d);
  }
  while (l * (1 + EPS) < r && l + EPS < r) {
    double mid = (l + r) / 2;
    vector<Interval> o;
    vector<Stage> b;
    for (int i = 0; i < n; ++i) {
      if (p[i].d > mid) {
        Interval in = get_interval(mid, p[i]);
        b.push_back(Stage{in.l, (int)o.size() * 2, true});
        b.push_back(Stage{in.r, (int)o.size() * 2 + 1, true});
        o.push_back(in);
        if (in.l < 0) {
          in.l += 2 * PI;
          in.r += 2 * PI;
          b.push_back(Stage{in.l, (int)o.size() * 2, false});
          b.push_back(Stage{in.r, (int)o.size() * 2 + 1, false});
          o.push_back(in);
        }
      }
    }
    LL cnt = 1LL * n * (n - 1) / 2;
    if (o.size() == 0) {
      r = mid;
      continue;
    }
    sort(b.begin(), b.end(),
         [](const Stage& a, const Stage& b) { return a.l < b.l; });
    BIT bit(b.size() + 10);
    vector<int> s(o.size());
    for (int i = 0; i < b.size(); ++i) {
      int t = b[i].a / 2;
      if (b[i].a & 1) {
        if (b[i].count) {
          cnt -= bit.query(i + 1) - bit.query(s[t]);
        }
        bit.add(s[t], -1);
      } else {
        s[t] = i + 1;
        bit.add(s[t], 1);
      }
    }
    if (cnt >= k)
      r = mid;
    else
      l = mid;
  }
  cout << fixed << setprecision(8) << l << endl;
  return 0;
}
