#include <bits/stdc++.h>
using namespace std;
const int N = 200100;
const double pi = acos(-1);
const double eps = 1e-9;
int x[N], y[N], n, tot, vis[N];
long long k;
struct node {
  double x;
  int id;
  node(double _x = 0.0, int _id = 0) : x(_x), id(_id) {}
  friend bool operator<(node a, node b) { return a.x < b.x; }
} a[N * 2];
int c[N];
void ins(int x, int val) {
  for (; x < N; x += x & (-x)) c[x] += val;
}
int sum(int x) {
  int res = 0;
  for (; x; x -= x & (-x)) res += c[x];
  return res;
}
long long calc(double ans) {
  tot = 0;
  for (int i = 1; i <= n; i++)
    if (ans < sqrt(x[i] * x[i] + y[i] * y[i])) {
      double tmp1 = atan2(y[i], x[i]);
      double tmp2 = acos(ans / sqrt(x[i] * x[i] + y[i] * y[i]));
      if (tmp1 - tmp2 > -pi)
        a[++tot] = node(tmp1 - tmp2, i);
      else
        a[++tot] = node(tmp1 - tmp2 + 2 * pi, i);
      if (tmp1 + tmp2 < pi)
        a[++tot] = node(tmp1 + tmp2, i);
      else
        a[++tot] = node(tmp1 + tmp2 - 2 * pi, i);
    }
  sort(a + 1, a + tot + 1);
  long long res = (long long)n * (n - 1) / 2;
  memset(c, 0, sizeof(c));
  memset(vis, 0, sizeof(vis));
  for (int i = 1; i <= tot; i++)
    if (!vis[a[i].id]) {
      vis[a[i].id] = i;
      ins(i, 1);
    } else {
      res -= sum(i) - sum(vis[a[i].id]);
      ins(vis[a[i].id], -1);
    }
  return res;
}
int main() {
  scanf("%d%lld", &n, &k);
  double l = 0, r = 1e5;
  for (int i = 1; i <= n; i++) scanf("%d%d", x + i, y + i);
  while (r - l > eps) {
    double mid = (l + r) / 2;
    if (calc(mid) >= k)
      r = mid;
    else
      l = mid;
  }
  printf("%.10lf\n", l);
}
