#include <iostream>
#include <algorithm>
#include <cmath>
#include <cstdio>
#define rep(i, n) for(i = 0; i < n; i++)
#define int long long
using namespace std;

void chmin(double &a, double b) { a = min(a, b); }

int INF = 1e+18;
int n, K;
int x[15], y[15];
double dp[1 << 15][15][15];

double dist(int a, int b) {
	double dx = x[a] - x[b];
	double dy = y[a] - y[b];
	return sqrt(dx * dx + dy * dy);
}

signed main() {
	int i, j, k, l;

	cin >> n >> K;
	rep(i, n) cin >> x[i + 1] >> y[i + 1];
	n += 1;

	rep(i, (1 << n)) rep(j, n) rep(k, K + 1) dp[i][j][k] = INF;

	dp[1][0][K] = 0;
	rep(i, (1 << n)) {
		rep(j, n) {
			rep(k, K + 1) {
				if (dp[i][j][k] >= INF) continue;
				rep(l, n) {
					if ((i >> l) % 2) continue;
					if (k > 0) {
						chmin(dp[i + (1 << l)][l][k - 1], dp[i][j][k] + dist(j, l));
					}
					chmin(dp[i + (1 << l)][l][K - 1], dp[i][j][k] + dist(j, 0) + dist(0, l));
				}
			}
		}
	}

	double ans = INF;
	rep(i, n) {
		rep(j, K + 1) {
			chmin(ans, dp[(1 << n) - 1][i][j] + dist(i, 0));
		}
	}

	printf("%.14f\n", ans);
	return 0;
}