#include <bits/stdc++.h>

using namespace std;

const int MAXN = 20, MAXX = (1 << 15);

int k, n;
double ans = 1e9, dp[MAXN][MAXN][MAXX];

struct E{
  int x, y;
} a[MAXN];

double C(int x, int y, int _x, int _y){
  return sqrt((x - _x) * (x - _x) + (y - _y) * (y - _y));
}
int main(){
  cin >> n >> k;
  a[0] = {0, 0};
  for(int i = 1; i <= n; i++){
    cin >> a[i].x >> a[i].y;
  }

  for(int i = 0; i <= n; i++){
    for(int j = 0; j <= n; j++){
      for(int k = 0; k < (1 << (n + 1)); k++){
        dp[i][j][k] = 1e9;
      }
    }
  }

  dp[0][k][1] = 0;
  for(int j = 1; j < (1 << (n + 1)); j++){
    for(int i = 1; i <= n; i++){
      if((j >> i & 1)) continue;
      for(int kk = 0; kk <= n; kk++){
        if(!(j >> kk & 1)) continue;
        for(int sy = 0; sy <= k; sy++){
          if(!sy){
            dp[i][k][j | (1 << i)] = min(dp[i][k][j | (1 << i)], dp[kk][sy][j] + C(a[i].x, a[i].y, 0, 0) + C(0, 0, a[kk].x, a[kk].y));
          } else {
            dp[i][sy - 1][j | (1 << i)] = min(dp[i][sy - 1][j | (1 << i)], dp[kk][sy][j] + C(a[i].x, a[i].y, a[kk].x, a[kk].y));
          }
        }
      }
    }
  }

  for(int j = 1; j <= n; j++){
    for(int i = 0; i <= k; i++){
      ans = min(ans, dp[j][i][(1 << (n + 1)) - 1] + C(0, 0, a[j].x, a[j].y));
    }
  }

  cout << fixed << setprecision(11) << ans;
  return 0;
}