import java.util.Arrays;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int k = sc.nextInt();
		int[] x = new int[n + 1];
		int[] y = new int[n + 1];
		for (int i = 0; i < n; i++) {
			x[i] = sc.nextInt();
			y[i] = sc.nextInt();
		}
		sc.close();

		double inf = 1e18;
		int n2 = 1 << n;
		double[][][] dp = new double[n2][n + 1][k + 1];
		for (int i = 0; i < n2; i++) {
			for (int j = 0; j <= n; j++) {
				Arrays.fill(dp[i][j], inf);
			}
		}
		dp[0][n][k] = 0;

		double[][] d = new double[n + 1][n + 1];
		for (int i = 0; i <= n; i++) {
			for (int j = i + 1; j <= n; j++) {
				d[i][j] = d[j][i] = Math.hypot(x[i] - x[j], y[i] - y[j]);
			}
		}

		for (int i = 0; i < n2; i++) {
			for (int j = 0; j < n; j++) {
				if ((i >> j & 1) == 1) {
					for (int j2 = 0; j2 < n; j2++) {
						if ((i >> j2 & 1) == 0) {
							int ni = i | (1 << j2);
							for (int a = 1; a < k; a++) {
								double alt = dp[i][j][a] + d[j][j2];
								dp[ni][j2][a - 1] = Math.min(dp[ni][j2][a - 1], alt);
							}
						}
					}
					for (int a = 0; a < k; a++) {
						double alt = dp[i][j][a] + d[j][n];
						dp[i][n][k] = Math.min(dp[i][n][k], alt);
					}
				}
			}
			for (int j2 = 0; j2 < n; j2++) {
				if ((i >> j2 & 1) == 0) {
					int ni = i | (1 << j2);
					double alt = dp[i][n][k] + d[n][j2];
					dp[ni][j2][k - 1] = Math.min(dp[ni][j2][k - 1], alt);
				}
			}
		}

		System.out.println(dp[n2 - 1][n][k]);
	}
}