import math

def dist(p, q):
    x1, y1 = p
    x2, y2 = q
    return math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2)
from functools import lru_cache
@lru_cache
def calc(pizza,pos,bits):
	if pizza==0:
		return calc(K,0,bits)+dist(dot[0],dot[pos])
	if bits==((1<<(N+1))-1):
		return dist(dot[0],dot[pos])
	ret=None
	if pizza!=K:
		ret=calc(K,0,bits)+dist(dot[0],dot[pos])
	for i in range(1,N+1):
		if not (bits>>i)&1:
			now=calc(pizza-1,i,bits|(1<<i))+dist(dot[i],dot[pos])
			if ret is None:
				ret=now
			ret=min(ret,now)
	return ret
	
N,K=map(int,input().split())
dot=[(0.0,0.0)]+[tuple(map(float,input().split())) for i in range(N)]
print(calc(K,0,1))