#include <bits/stdc++.h>
using namespace std;
const int N = 400000 + 10;
const double eps = 1e-9;
const double pi = acos(-1);
int n;
long long k;
struct Vec {
  int x, y;
  double d() { return x * x + y * y; }
} p[N];
vector<double> v;
int id(double x) { return lower_bound(v.begin(), v.end(), x) - v.begin() + 1; }
int bit[N];
void add(int x, int k) {
  while (x < N) {
    bit[x] += k;
    x += x & (-x);
  }
}
int sum(int x) {
  int ans = 0;
  while (x > 0) {
    ans += bit[x];
    x -= x & (-x);
  }
  return ans;
}
long long cal(vector<pair<double, double> > vec) {
  memset(bit, 0, sizeof(bit));
  sort(vec.begin(), vec.end());
  v.clear();
  for (auto p : vec) {
    v.push_back(p.first);
    v.push_back(p.second);
  }
  sort(v.begin(), v.end());
  v.erase(unique(v.begin(), v.end()), v.end());
  long long res = 0;
  for (auto p : vec) {
    res += sum(id(p.second)) - sum(id(p.first));
    add(id(p.second), 1);
  }
  return res;
}
double check(double x) {
  vector<pair<double, double> > vec;
  long long tot = 1LL * n * (n - 1) / 2, cnt = 0;
  for (int i = 1; i <= n; i++) {
    if (p[i].d() > x * x - eps) {
      double dis = sqrt(p[i].d());
      double theta = acos(x / dis);
      double mid = atan2(p[i].y, p[i].x);
      int pre = vec.size();
      if (mid < 0) mid += 2 * pi;
      if (mid + theta > 2 * pi) {
        vec.push_back(make_pair(mid + theta - 2 * pi, mid - theta));
      } else if (mid - theta < 0) {
        vec.push_back(make_pair(mid + theta, mid - theta + 2 * pi));
      } else {
        vec.push_back(make_pair(mid - theta, mid + theta));
      }
      int cur = vec.size();
    }
  }
  tot -= cal(vec);
  return tot >= k;
}
int main() {
  scanf("%d%lld", &n, &k);
  for (int i = 1; i <= n; i++) {
    scanf("%d%d", &p[i].x, &p[i].y);
  }
  double lef = 0, rig = 2e4;
  for (int i = 1; i <= 100; i++) {
    double mid = (lef + rig) / 2;
    if (check(mid))
      rig = mid;
    else
      lef = mid;
  }
  printf("%.8f\n", rig);
}
