#include <iostream>
#include <vector>
#include <cmath>
#include <unordered_map>
#include <tuple>
#include <limits>
#include <map>
#include<bits/stdc++.h>

using namespace std;

int N, K;
vector<pair<double, double>> dot;

// ユークリッド距離を計算する関数
double dist(const pair<double, double>& p, const pair<double, double>& q) {
    double x1 = p.first, y1 = p.second;
    double x2 = q.first, y2 = q.second;
    return sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1));
}

// メモ化用のunordered_map
map<tuple<int, int, int>, double> memo;

// メモ化された再帰関数
double calc(int pizza, int pos, int bits) {
    if (memo.find(make_tuple(pizza, pos, bits)) != memo.end()) {
        return memo[make_tuple(pizza, pos, bits)];
    }

    double ret;
    if (pizza == 0) {
        ret = calc(K, 0, bits) + dist(dot[0], dot[pos]);
    } else if (bits == ((1 << (N + 1)) - 1)) {
        ret = dist(dot[0], dot[pos]);
    } else {
        ret = numeric_limits<double>::max();
        if (pizza != K) {
            ret = min(ret, calc(K, 0, bits) + dist(dot[0], dot[pos]));
        }
        for (int i = 1; i <= N; ++i) {
            if (!((bits >> i) & 1)) {
                double now = calc(pizza - 1, i, bits | (1 << i)) + dist(dot[i], dot[pos]);
                ret = min(ret, now);
            }
        }
    }

    memo[make_tuple(pizza, pos, bits)] = ret;
    return ret;
}

int main() {
    cin >> N >> K;
    dot.emplace_back(0.0, 0.0);
    for (int i = 0; i < N; ++i) {
        double x, y;
        cin >> x >> y;
        dot.emplace_back(x, y);
    }
    std::cout << std::fixed << std::setprecision(16);
    cout << calc(K, 0, 1) << endl;
    return 0;
}