#include <bits/stdc++.h>
using namespace std;
const int c = 200002;
int w, kezd[c], veg[c], t[c];
long long sum, n, k;
vector<pair<long double, int> > sz;
long double x[c], y[c], lo = 0, hi = 2e4, mid, eps = 1e-7;
void pb(long double a, long double b, int i) {
  if (b > 0) {
    sz.push_back({a, i});
  } else {
    sz.push_back({c - a, i});
  }
}
int lsb(int a) { return (a & (-a)); }
void add(int a, int b) {
  while (a < c) {
    t[a] += b;
    a += lsb(a);
  }
}
int ask(int a) {
  int sum = 0;
  while (a) {
    sum += t[a];
    a -= lsb(a);
  }
  return sum;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin >> n >> k;
  k = n * (n - 1) / 2 - k;
  for (int i = 1; i <= n; i++) {
    cin >> x[i] >> y[i];
  }
  while (hi - lo > eps) {
    mid = (hi + lo) / 2;
    sum = 0;
    sz.clear();
    for (int i = 1; i <= n; i++) {
      long double dist = sqrt((x[i] * x[i] + y[i] * y[i]));
      if (dist > mid) {
        long double r = (sqrt(dist * dist - mid * mid)),
                    p = (mid * mid) / (mid * mid + r * r),
                    ert = sqrt(mid * mid / dist / dist - p * p);
        long double xx = p * x[i], yy = p * y[i], v1 = ert * y[i],
                    v2 = ert * x[i];
        pb(xx + v1, yy - v2, i);
        pb(xx - v1, yy + v2, i);
      }
    }
    for (int i = 1; i <= n; i++) {
      kezd[i] = veg[i] = 0;
    }
    sort(sz.begin(), sz.end());
    int si = sz.size();
    for (int i = 0; i < si; i++) {
      int id = sz[i].second;
      if (!kezd[id]) {
        kezd[id] = i + 1;
      } else {
        veg[id] = i + 1;
      }
    }
    for (int i = 0; i < si; i++) {
      int id = sz[i].second;
      if (kezd[id] == i + 1) {
        sum += ask(veg[id]);
        add(veg[id], 1);
      } else {
        add(veg[id], -1);
      }
    }
    if (sum > k) {
      lo = mid;
    } else {
      hi = mid;
    }
  }
  cout.precision(10);
  cout << lo << "\n";
  return 0;
}
