#include <iostream>
#include <iomanip>
#include <cassert>
#include <vector>
#include <cmath>
#include <bit>
#include <random>

int main() {
    std::cin.tie(nullptr)->sync_with_stdio(false);
    
    std::mt19937 mt{std::random_device{}()};
    // while (true) {
        int N, K;
        // N = mt() % 5 + 1;
        // K = mt() % N + 1;
        std::cin >> N >> K;
        std::vector<int> X(N), Y(N);
        // std::cerr << N << ' ' << K << std::endl;
        // for (int i{} ; i < N ; i++) {
        //     X[i] = mt() % (int)2e9 - 1e9;
        //     Y[i] = mt() % (int)2e9 - 1e9;
        //     std::cerr << X[i] << ' ' << Y[i] << std::endl;
        // }
        for (int i{} ; i < N ; i++) std::cin >> X[i] >> Y[i];
        const long double INF{(long double)1e18};
        std::vector dp(N, std::vector<long double>(1 << N, INF));
        for (int i{} ; i < N ; i++) {
            dp[i][1 << i] = sqrtl((long double)X[i] * X[i] + (long double)Y[i] * Y[i]);
        }
        for (int bit{} ; bit < (1 << N) ; bit++) {
            for (int s{} ; s < N ; s++) if (bit & (1 << s)) {
                for (int t{} ; t < N ; t++) if (!(bit & (1 << t))) {
                    if (dp[s][bit] > 1e15) continue;
                    int dx{X[s] - X[t]}, dy{Y[s] - Y[t]};
                    dp[t][bit | (1 << t)] = std::min(dp[t][bit | (1 << t)], dp[s][bit] + sqrtl((long double)dx * dx + (long double)dy * dy));
                    // std::cout << s << ' ' << bit << " -> " << t << ' ' << dp[s][bit] << std::endl;
                }
            }
        }
        std::vector<long double> cost(1 << N, INF);
        cost[0] = 0;
        for (int bit{} ; bit < (1 << N) ; bit++) for (int i{} ; i < N ; i++) if (bit & (1 << i)) {
            if (dp[i][bit] > 1e15) continue;
            cost[bit] = std::min(cost[bit], dp[i][bit] + sqrtl((long double)X[i] * X[i] + (long double)Y[i] * Y[i]));
        }
        for (int bit{} ; bit < (1 << N) ; bit++) assert(cost[bit] < 1e15);
        std::vector<long double> ep(1 << N, INF);
        ep[0] = 0;
        int all{(1 << N) - 1};
        for (int bit{} ; bit < (1 << N) ; bit++) {
            // assert(ep[bit] < 1e15);
            int can{all ^ bit};
            for (int mask{can} ; mask ; mask = (mask - 1) & can) {
                if ((int)std::popcount((unsigned)mask) <= K) {
                    assert((bit & mask) == 0);
                    ep[bit | mask] = std::min(ep[bit | mask], ep[bit] + cost[mask]);
                }
            }
        }
        std::cout << std::fixed << std::setprecision(8) << ep[all] << '\n';
    // }
}