import sys

# sys.setrecursionlimit(200005)
# sys.set_int_max_str_digits(200005)
int1 = lambda x: int(x)-1
pDB = lambda *x: print(*x, end="\n", file=sys.stderr)
p2D = lambda x: print(*x, sep="\n", end="\n\n", file=sys.stderr)
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def SI(): return sys.stdin.readline().rstrip()

dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
# dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
# inf = -1-(-1 << 31)
inf = -1-(-1 << 62)

# md = 10**9+7
md = 998244353

from collections import defaultdict
from heapq import *

def norm(i, j):
    x, y = xy[i]
    p, q = xy[j]
    return ((x-p)**2+(y-q)**2)**0.5

n, k = LI()
xy = LLI(n)
dist = defaultdict(lambda: inf)
hp = []
for i, (x, y) in enumerate(xy):
    s = 1 << i
    d = (x**2+y**2)**0.5
    sir = s << 8 | i << 4 | k-1
    heappush(hp, (d, sir))
    dist[sir] = d
xy.append([0, 0])
ans=inf
while hp:
    d, sir = heappop(hp)
    if dist[sir] < d: continue
    si, r = divmod(sir, 16)
    s, i = divmod(si, 16)
    if s+1 == 1 << n:
        ans=min(ans,d+norm(i,n))
        continue
    for j in range(n):
        if s >> j & 1: continue
        ns = s | 1 << j
        nd = d+norm(i, n)+norm(j, n)
        v = ns << 8 | j << 4 | k-1
        if nd < dist[v]:
            dist[v] = nd
            heappush(hp, (nd, v))
        if r:
            nd = d+norm(i, j)
            v = ns << 8 | j << 4 | r-1
            if nd < dist[v]:
                dist[v] = nd
                heappush(hp, (nd, v))

print(ans)