#include <bits/stdc++.h>
using namespace std;
class point {
 public:
  long double x, y;
  long double SZ() { return sqrtl(x * x + y * y); }
};
const long double PI = acosl(-1.0);
void Go(long double &t) {
  while (t < -PI) t += PI * 2;
  while (t > PI) t -= PI * 2;
}
struct AA {
  long double d;
  int num;
  bool operator<(const AA &p) const { return d < p.d; }
} U[201000];
void Add(int BIT[], int k, int a, int b) {
  a++;
  while (a < k) {
    BIT[a] += b;
    a += (a & -a);
  }
}
int Sum(int BIT[], int a) {
  a++;
  int r = 0;
  while (a) {
    r += BIT[a];
    a -= (a & -a);
  }
  return r;
}
void init(int BIT[], int k) {
  for (int i = 0; i < k; i++) BIT[i] = 0;
}
long long Get(long double r, point w[], int n) {
  int BB[n + 1][2], CC[n + 1];
  int BIT[2 * n + 1];
  init(BIT, 2 * n + 1);
  int i;
  int c = 0;
  for (i = 1; i <= n; i++) {
    long double d = w[i].SZ();
    if (d <= r) continue;
    long double an = atan2l(w[i].y, w[i].x);
    long double z = acosl(r / d);
    long double b = an - z, e = an + z;
    Go(b);
    Go(e);
    U[c++] = {b, i};
    U[c++] = {e, i};
  }
  sort(U, U + c);
  for (i = 1; i <= n; i++) CC[i] = 0;
  for (i = 0; i < c; i++) BB[U[i].num][CC[U[i].num]++] = i;
  init(BIT, 2 * n + 1);
  long long s = 0;
  for (i = 0; i < c; i++) {
    int x = U[i].num;
    if (BB[x][0] == i) {
      s += Sum(BIT, BB[x][1]) - Sum(BIT, i);
      Add(BIT, 2 * n + 1, BB[x][1], 1);
    }
  }
  return 1ll * n * (n - 1) / 2 - s;
}
int main() {
  int n;
  long long K;
  cin >> n >> K;
  point w[n + 1];
  for (int i = 1; i <= n; i++) cin >> w[i].x >> w[i].y;
  long double b = 0.0, e = 1e5;
  for (int i = 0; i < 50; i++) {
    long double mid = (b + e) * 0.5;
    if (Get(mid, w, n) >= K)
      e = mid;
    else
      b = mid;
  }
  cout.precision(10);
  cout << fixed << (b + e) * 0.5;
  return 0;
}
