#include <bits/stdc++.h>
using namespace std;
mt19937 rng(static_cast<unsigned int>(
    chrono::steady_clock::now().time_since_epoch().count()));
template <typename num_t>
inline void add_mod(num_t& a, const long long& b, const int& m) {
  a = (a + b) % m;
  if (a < 0) a += m;
}
template <typename num_t>
inline void unsafe_add_mod(num_t& a, const long long& b, const int& m) {
  a += b;
  if (a < 0)
    a += m;
  else if (a >= m)
    a -= m;
}
template <typename num_t>
inline bool update_max(num_t& a, const num_t& b) {
  return a < b ? a = b, true : false;
}
template <typename num_t>
inline bool update_min(num_t& a, const num_t& b) {
  return a > b ? a = b, true : false;
}
template <typename num_t>
num_t gcd(const num_t& lhs, const num_t& rhs) {
  return !lhs ? rhs : gcd(rhs % lhs, lhs);
}
template <typename num_t>
num_t lcm(const num_t& lhs, const num_t& rhs) {
  return lhs / ::gcd(lhs, rhs) * rhs;
}
template <typename num_t>
num_t pw(num_t n, num_t k, const num_t& mod) {
  if (k == -1) k = mod - 2;
  num_t res = 1;
  for (; k > 0; k >>= 1) {
    if (k & 1) res = 1ll * res * n % mod;
    n = 1ll * n * n % mod;
  }
  return res % mod;
}
const int inf = 1e9 + 7;
const int mod = 998244353;
const long long ll_inf = (long long)1000000000000ll + 7;
const int maxn = 5000 + 7;
void solve() {
  int n, k;
  cin >> n >> k;
  vector<pair<int, int>> points(n);
  for (auto& p : points) cin >> p.first >> p.second;
  auto sqr = [](long long u) -> long long { return u * u; };
  map<pair<int, int>, vector<double>> mapping;
  for (auto p : points)
    if (p.first != 0 || p.second != 0) {
      int d = gcd(abs(p.first), abs(p.second));
      double dist = sqrt(sqr(p.first) + sqr(p.second));
      mapping[{p.first / d, p.second / d}].push_back(dist);
    }
  if ((int)(mapping).size() == 1) {
    vector<double> cur = mapping.begin()->second;
    cur.push_back(0);
    sort(cur.begin(), cur.end());
    vector<double> dp(cur.size() + 1);
    for (int i = 0; i < k; ++i) {
      dp[i + 1] = dp[i];
      dp[i + 1] += cur[i] * i - cur[i] * (k - i - 1);
    }
    double best_ans = dp[k];
    double temp = 0;
    for (int i = (int)(cur).size() - 1, j = 0; j < k; --i, ++j) {
      temp += cur[i] * (k - j - 1) - cur[i] * j;
      update_max(best_ans, temp + dp[k - j - 1]);
    }
    cout << fixed << setprecision(9) << best_ans << '\n';
    return;
  }
  vector<double> best;
  double full_cost = 0;
  for (auto& p : mapping) {
    auto& cur = p.second;
    sort(cur.begin(), cur.end(), greater<double>());
    double temp = 0;
    for (int i = (0), _b = ((int)(cur).size()); i < _b; ++i) {
      temp = cur[i] * (k - i * 2 - 1);
      full_cost += temp;
      best.push_back(temp);
    }
  }
  sort(best.begin(), best.end(), greater<double>());
  double ans = 0;
  for (int i = (0), _b = (k); i < _b; ++i) ans += best[i];
  double best_ans = ans;
  for (auto& p : mapping) {
    auto& cur = p.second;
    auto cur_cost = full_cost;
    for (int i = (0), _b = ((int)(cur).size()); i < _b; ++i) {
      cur_cost -= cur[i] * (k - i * 2 - 1);
    }
    if (k <= n - (int)(cur).size()) continue;
    int remain = k - n + (int)(cur).size();
    vector<double> sum_right((int)(cur).size() + 1);
    for (int i = (int)(cur).size() - 1, j = 0; i >= 0; --i, ++j) {
      sum_right[j + 1] =
          cur[i] * (k - remain) + cur[i] * j - cur[i] * (remain - j - 1);
      sum_right[j + 1] += sum_right[j];
    }
    double temp = 0;
    for (int i = 0; i < remain; ++i) {
      temp += cur[i] * (k - remain) + cur[i] * (remain - i - 1) - cur[i] * i;
      update_max(best_ans, cur_cost + temp + sum_right[remain - i - 1]);
    }
  }
  cerr << "best_ans"
       << ": " << (best_ans) << '\n';
  ;
  cout << fixed << setprecision(9) << best_ans << '\n';
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  const bool multiple_test = false;
  int test = 1;
  if (multiple_test) cin >> test;
  for (int i = 0; i < test; ++i) {
    solve();
  }
}
