#include <bits/stdc++.h>
using namespace std;
const double Pi = acos(-1.0);
int n;
struct Point {
  int x, y;
  double a, d;
};
Point P[100005];
struct Node {
  double x, l, r;
  int n;
} A[100005 << 1];
bool cmp(Node a, Node b) { return a.x < b.x; }
int tre[100005];
int Update(int x, int v) {
  for (int i = x + 1; i <= n; i += i & -i) tre[i] += v;
  return 0;
}
int Getsum(int x) {
  int ret = 0;
  for (int i = x + 1; i; i -= i & -i) ret += tre[i];
  return ret;
}
double all[100005];
int main() {
  long long k;
  scanf("%d%lld", &n, &k);
  for (int i = 0; i < n; i++) {
    scanf("%d%d", &P[i].x, &P[i].y);
    P[i].a = atan2(P[i].y, P[i].x);
    P[i].d = sqrt(P[i].x * P[i].x + P[i].y * P[i].y);
  }
  double l = 0, r = 15000;
  for (int w = 1; w <= 40; w++) {
    double m = (l + r) / 2;
    long long num = 0;
    int c = 0, c2 = 0;
    for (int i = 0; i < n; i++) {
      if (P[i].d > m) {
        double t = acos(m / P[i].d);
        double a1 = P[i].a - t, a2 = P[i].a + t;
        while (a1 < -Pi) a1 += 2 * Pi;
        while (a2 > Pi) a2 -= 2 * Pi;
        if (a1 > a2) swap(a1, a2);
        A[c++] = (Node){a1, a2, a2, 0}, all[c2++] = a2;
        A[c++] = (Node){a1 - 1e-12, a1 + 1e-12, a2 - 1e-12, 1};
      }
    }
    fill(tre, tre + n + 1, 0);
    sort(A, A + c, cmp);
    sort(all, all + c2);
    for (int i = 0; i < c; i++) {
      if (A[i].n == 0) {
        int p = lower_bound(all, all + c2, A[i].l) - all;
        Update(p, 1);
      } else {
        int q = upper_bound(all, all + c2, A[i].r) - all - 1;
        int p = lower_bound(all, all + c2, A[i].l) - all;
        num += A[i].n * (Getsum(q) - Getsum(p - 1));
      }
    }
    num = (long long)n * (n - 1) / 2 - num;
    if (num < k)
      l = m;
    else
      r = m;
  }
  printf("%.12lf\n", l);
}
