#include <bits/stdc++.h>
using namespace std;
#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
using ll = long long;
constexpr int INF = 0x3f3f3f3f;
constexpr long long LINF = 0x3f3f3f3f3f3f3f3fLL;
constexpr double EPS = 1e-8;
constexpr int MOD = 998244353;
// constexpr int MOD = 1000000007;
constexpr int DY4[]{1, 0, -1, 0}, DX4[]{0, -1, 0, 1};
constexpr int DY8[]{1, 1, 0, -1, -1, -1, 0, 1};
constexpr int DX8[]{0, -1, -1, -1, 0, 1, 1, 1};
template <typename T, typename U>
inline bool chmax(T& a, U b) { return a < b ? (a = b, true) : false; }
template <typename T, typename U>
inline bool chmin(T& a, U b) { return a > b ? (a = b, true) : false; }
struct IOSetup {
  IOSetup() {
    std::cin.tie(nullptr);
    std::ios_base::sync_with_stdio(false);
    std::cout << fixed << setprecision(20);
  }
} iosetup;

int main() {
  int n, k; cin >> n >> k;
  vector<int> x(n + 1, 0), y(n + 1, 0); REP(i, n) cin >> x[i] >> y[i];
  const auto dist = [&](const int i, const int j) -> double {
    return hypot(x[i] - x[j], y[i] - y[j]);
  };
  vector dp1(1 << n, vector(n, static_cast<double>(LINF)));
  REP(i, n) dp1[1 << i][i] = dist(n, i);
  FOR(bit, 1, 1 << n) REP(i, n) {
    if ((bit >> i & 1) == 0) continue;
    REP(j, n) {
      if (bit >> j & 1) continue;
      chmin(dp1[bit | 1 << j][j], dp1[bit][i] + dist(i, j));
    }
  }
  vector<double> tm(1 << n, LINF);
  FOR(bit, 1, 1 << n) REP(i, n) chmin(tm[bit], dp1[bit][i] + dist(i, n));
  vector<double> dp2(1 << n, LINF);
  dp2[0] = 0;
  REP(bit, 1 << n) {
    const int rem = ((1 << n) - 1) ^ bit;
    for (int subset = rem; subset > 0;) {
      if (popcount(static_cast<unsigned>(subset)) <= k) {
        chmin(dp2[bit | subset], dp2[bit] + tm[subset]);
      }
      if ((subset = (subset - 1) & rem) == rem) break;
    }
  }
  cout << dp2.back() << '\n';
  return 0;
}