#include <bits/stdc++.h>
using namespace std;
const int N = 100010;
double dis[N], ang[N];
int tree[2 * N], n;
long long k;
pair<double, int> a[2 * N];
pair<int, int> b[N];
void add(int x, int k) {
  while (x <= 2 * n) {
    tree[x] += k;
    x += x & -x;
  }
}
int find(int x) {
  int ans = 0;
  while (x > 0) {
    ans += tree[x];
    x -= x & -x;
  }
  return ans;
}
bool check(double r) {
  int m = 0;
  long long sum = 0;
  for (int i = 1; i <= n; i++)
    if (r < dis[i]) {
      double s = acos(r / dis[i]);
      double s1 = ang[i] - s, s2 = ang[i] + s;
      if (s1 < 0) s1 += 2 * 3.14159265358979323846;
      if (s2 > 2 * 3.14159265358979323846) s2 -= 2 * 3.14159265358979323846;
      if (s1 > s2) swap(s1, s2);
      a[m++] = {s1, -i};
      a[m++] = {s2, i};
    }
  if (m) {
    sort(a, a + m);
    for (int i = 1; i <= n; i++) b[i] = {1, 0};
    for (int i = 0; i < m; i++) {
      if (a[i].second > 0)
        b[a[i].second].second = i + 1;
      else
        b[-a[i].second].first = i + 1;
    }
    m = 0;
    for (int i = 1; i <= n; i++)
      if (b[i].first < b[i].second) {
        b[m++] = b[i];
      }
    sort(b, b + m);
    memset(tree, 0, sizeof tree);
    for (int i = m - 1; i >= 0; i--) {
      sum += find(b[i].second);
      add(b[i].first, 1);
      add(b[i].second, -1);
    }
  }
  return ((long long)n * (n - 1) / 2 - sum >= k);
}
int main() {
  scanf("%d %lld", &n, &k);
  int x, y;
  for (int i = 1; i <= n; i++) {
    scanf("%d %d", &x, &y);
    dis[i] = sqrt(x * x + y * y);
    ang[i] = atan2(y, x);
    if (ang[i] < 0) ang[i] += 2 * 3.14159265358979323846;
  }
  double l = 0, r = 20000;
  while (r - l > 1e-8) {
    double mid = (r + l) / 2;
    if (check(mid))
      r = mid;
    else
      l = mid;
  }
  printf("%.8lf\n", l);
  return 0;
}
