#include <stdio.h>

typedef struct {
	double x, y;
} point;

// The distance between p and q
double distance(point p, point q)
{
	return sqrt((p.x - q.x) * (p.x - q.x) + (p.y - q.y) * (p.y - q.y));
}

const int bit[21] = {1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768, 65536, 131072, 262144, 524288, 1048576};

void chmin(double *a, double b)
{
	if (*a > b) *a = b;
}

int main()
{
	int i, N, K;
	point p[15];
	scanf("%d %d", &N, &K);
	for (i = 0, p[N].x = 0.0, p[N].y = 0.0; i < N; i++) scanf("%lf %lf", &(p[i].x), &(p[i].y));
	
	int j, k, ii;
	double dp[16384][15][15], dist[15][15];
	const double sup = 1e+16;
	for (k = 0; k < bit[N]; k++) for (i = 0; i <= N; i++) for (j = 0; j <= K; j++) dp[k][i][j] = sup;
	for (i = 0; i <= N; i++) for (j = 0; j <= N; j++) dist[i][j] = distance(p[i], p[j]);
	for (k = 0, dp[0][N][K] = 0.0; k < bit[N]; k++) {
		for (i = 0; i <= N; i++) {
			chmin(&(dp[k][N][K]), dp[k][i][0] + dist[i][N]);
			for (j = 1; j <= K; j++) {
				if (dp[k][i][j] == sup) continue;
				for (ii = 0; ii < N; ii++) chmin(&(dp[k | bit[ii]][ii][j-1]), dp[k][i][j] + dist[i][ii]);
				chmin(&(dp[k][N][K]), dp[k][i][j] + dist[i][N]);
			}
		}
	}
	printf("%.7lf\n", dp[bit[N]-1][N][K]);
	fflush(stdout);
	return 0;
}