/* -*- coding: utf-8 -*-
 *
 * 2955.cc:  No.2955 Pizza Delivery Plan - yukicoder
 */

#include<cstdio>
#include<cmath>
#include<algorithm>

using namespace std;

/* constant */

const int MAX_N = 14;
const int NBITS = 1 << MAX_N;
const double DINF = 1e60;

/* typedef */

/* global variables */

int xs[MAX_N], ys[MAX_N];
double es[MAX_N][MAX_N], oes[MAX_N];
int bnums[NBITS];
double dp[NBITS][MAX_N][MAX_N + 1];

/* subroutines */

inline double dist(double dx, double dy) {
  return sqrt(dx * dx + dy * dy);
}

inline void setmin(double &a, double b) { if (a > b) a = b; }

/* main */

int main() {
  int n, k;
  scanf("%d%d", &n, &k);
  for (int i = 0; i < n; i++) scanf("%d%d", xs + i, ys + i);

  for (int i = 0; i < n; i++) {
    oes[i] = dist(xs[i], ys[i]);
    es[i][i] = 0.0;
    for (int j = i + 1; j < n; j++)
      es[i][j] = es[j][i] = dist(xs[j] - xs[i], ys[j] - ys[i]);
  }

  int nbits = 1 << n;
  for (int bits = 1, msb = 1; bits < nbits; bits++) {
    if ((msb << 1) <= bits) msb <<= 1;
    bnums[bits] = bnums[bits ^ msb] + 1;
  }

  for (int bits = 0; bits < nbits; bits++)
    for (int i = 0; i < n; i++)
      fill(dp[bits][i], dp[bits][i] + k + 1, DINF);

  for (int i = 0; i < n; i++) dp[1 << i][i][1] = oes[i];

  for (int bits = 0; bits < nbits; bits++) {
    for (int i = 0; i < n; i++)
      for (int j = 1; j <= k; j++)
	if (dp[bits][i][j] < DINF) {
	  for (int i1 = 0, bi = 1; i1 < n; i1++, bi <<= 1)
	    if (! (bits & bi)) {
	      setmin(dp[bits | bi][i1][1],
		     dp[bits][i][j] + oes[i] + oes[i1]);
	      if (j < k)
		setmin(dp[bits | bi][i1][j + 1],
		       dp[bits][i][j] + es[i][i1]);
	    }
	}
  }

  double mind = DINF;
  for (int i = 0; i < n; i++)
    for (int j = 1; j <= k; j++)
      setmin(mind, dp[nbits - 1][i][j] + oes[i]);

  printf("%.11lf\n", mind);
  
  return 0;
}