#include <bits/stdc++.h>
using namespace std;
template <class T>
using vc = vector<T>;
template <class T>
using vvc = vc<vc<T>>;
template <class T>
void mkuni(vector<T> &v) {
  sort(v.begin(), v.end());
  v.erase(unique(v.begin(), v.end()), v.end());
}
long long rand_int(long long l, long long r) {
  static mt19937_64 gen(chrono::steady_clock::now().time_since_epoch().count());
  return uniform_int_distribution<long long>(l, r)(gen);
}
template <class T>
void print(T x, int suc = 1) {
  cout << x;
  if (suc == 1)
    cout << '\n';
  else
    cout << ' ';
}
int topbit(signed t) { return t == 0 ? -1 : 31 - __builtin_clz(t); }
int topbit(long long t) { return t == 0 ? -1 : 63 - __builtin_clzll(t); }
template <class t>
struct BIT {
  vc<t> buf;
  int s;
  BIT(int n = 0) { init(n); }
  void init(int n) { buf.assign(s = n, 0); }
  void add(int i, t v) {
    for (; i < s; i += (i + 1) & (-i - 1)) buf[i] += v;
  }
  t get(int i) {
    t res = 0;
    for (; i >= 0; i -= (i + 1) & (-i - 1)) res += buf[i];
    return res;
  }
  t sum(int b, int e) { return get(e - 1) - get(b - 1); }
  int kth(int k) {
    int res = 0;
    for (int i = topbit(s); i >= 0; i--) {
      int w = res + (1 << i);
      if (w <= s && buf[w - 1] <= k) {
        k -= buf[w - 1];
        res = w;
      }
    }
    return res;
  }
  int kth_helper(int k, int i) { return kth(k + get(i - 1)); }
};
struct P {
  double x, y;
};
int n;
long long k;
double solve(double x, vc<P> &a) {
  long long ans = 1ll * n * (n - 1) / 2;
  vc<P> b;
  for (auto &p : a) {
    if (p.x * p.x + p.y * p.y - x * x > 1e-6) b.emplace_back(p);
  }
  vc<pair<double, int>> all;
  int cnt = 1;
  for (auto &p : b) {
    double dis = sqrt(p.x * p.x + p.y * p.y);
    double angle = acos(x / dis);
    double pre = atan2(p.y, p.x);
    double now1 = pre + angle, now2 = pre - angle;
    if (now2 < -acos(-1)) now2 += 2 * acos(-1);
    if (now1 > acos(-1)) now1 -= 2 * acos(-1);
    if (now1 > now2) swap(now1, now2);
    all.emplace_back(now1, cnt);
    all.emplace_back(now2, -cnt);
    ++cnt;
  }
  vc<pair<int, int>> pos(b.size() + 1);
  BIT<int> bit(all.size() + 1);
  sort(all.begin(), all.end());
  for (int i = 0; i < all.size(); ++i) {
    int se = all[i].second;
    if (se > 0)
      pos[se].first = i;
    else
      pos[-se].second = i;
  }
  for (int i = 0; i < all.size(); ++i) {
    int se = all[i].second;
    if (se > 0) {
      bit.add(pos[se].first, 1);
    } else {
      ans -= bit.get(pos[-se].second) - bit.get(pos[-se].first);
      bit.add(pos[-se].first, -1);
    }
  }
  return ans;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cin >> n >> k;
  vc<P> aa(n);
  for (int i = 0; i < n; ++i) cin >> aa[i].x >> aa[i].y;
  double l = 0, r = 1e9;
  int T = 100;
  while (T--) {
    double mid = (l + r) / 2;
    if (solve(mid, aa) >= k)
      r = mid;
    else
      l = mid;
  }
  cout << fixed << setprecision(10) << r << '\n';
}
