R=range
J=lambda:map(int,input().split())
N,K=J()
v=[list(J())for i in R(N)]+[[0,0]]
M=N+1
w=[[0]*M for i in R(M)]
for i in R(M):
	for j in R(i,M):w[i][j]=w[j][i]=((v[i][0]-v[j][0])**2+(v[i][1]-v[j][1])**2)**0.5
S=R(1<<N)
D=[[[9.0**30]*(K+1)for i in R(M)]for p in S]
D[0][N][K]=0
for p in S:
	for i in R(N):
		if(p>>i)&1:
			q=p^(1<<i);D[p][i][K-1]=D[q][N][K]+w[N][i]
			for j in R(N):
				if(q>>j)&1:
					for k in R(K):D[p][i][k]=min(D[p][i][k],D[q][j][k+1]+w[j][i])
	for j in R(N):
		if(p>>j)&1:
			for k in R(K):D[p][N][K]=min(D[p][N][K],D[p][j][k]+w[j][N])
print(D[(1<<N)-1][N][K])