#include<bits/stdc++.h>
namespace {
#pragma GCC diagnostic ignored "-Wunused-function"
#include<atcoder/all>
#pragma GCC diagnostic warning "-Wunused-function"
using namespace std;
using namespace atcoder;
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; i--)
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
template<class T> bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; } else return false; }
template<class T> bool chmin(T& a, const T& b) { if (b < a) { a = b; return true; } else return false; }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;

double dp[1 << 15][15][15];
double dist[15][15];

} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n, k;
  cin >> n >> k;
  vector<P> xy(n);
  for (auto& [x, y] : xy) cin >> x >> y;
  xy.insert(xy.begin(), 1, pair(0, 0));
  rep(i, n + 1) rep(j, n + 1) {
    int dx = xy[i].first - xy[j].first;
    int dy = xy[i].second - xy[j].second;
    dist[i][j] = sqrt(ll(dx) * dx + ll(dy) * dy);
  }
  constexpr double inf = 1e20;
  rep(s, 1 << 15) rep(v, 15) rep(kv, 15) dp[s][v][kv] = inf;
  dp[1][0][k] = 0;
  rep(s, 1 << (n + 1)) {
    rep(u, n + 1) rep(ku, k + 1) {
      chmin(dp[s][0][k], dp[s][u][ku] + dist[u][0]);
    }
    rep(u, n + 1) rep(ku, k + 1) if (ku) rep(v, n + 1) {
      chmin(dp[s | 1 << v][v][ku - 1], dp[s][u][ku] + dist[u][v]);
    }
  }
  cout << fixed << setprecision(12) << dp[(1 << (n + 1)) - 1][0][k] << '\n';
}