N,K=map(int, input().split())

D=[[-1]*(N+1) for i in range(N+1)]

A=[(0,0)]
for i in range(N):
  x,y=map(int, input().split())
  A.append((x,y))
  
for i in range(N+1):
  for j in range(N+1):
    x=A[i][0]-A[j][0]
    y=A[i][1]-A[j][1]
    D[i][j]=(x**2+y**2)**.5

dp=[[[10**20]*(1<<N) for i in range(N+1)] for j in range(K+1)]
from collections import deque
d=deque()
d.append((0,0,K))
dp[K][0][0]=0
while d:
  now,bit,c=d.popleft()
  for i in range(N):
    if not (bit & (1<<i)):
      bbit=bit^(1<<i)
      if dp[c-1][i+1][bbit]>dp[c][now][bit]+D[now][i+1] and c>1:
        dp[c-1][i+1][bbit]=dp[c][now][bit]+D[now][i+1]
        d.append((i+1,bbit,c-1))
      if dp[K][0][bbit]>dp[c][now][bit]+D[now][i+1]+D[i+1][0]:
        dp[K][0][bbit]=dp[c][now][bit]+D[now][i+1]+D[i+1][0]
        d.append((0,bbit,K))
      
print(dp[K][0][-1])