import math

INF = 1.0e15

n, k = map(int, input().split())
points = [tuple(map(int, input().split())) for _ in range(n)]
points.append((0, 0))

dist = [[INF for _ in range(n + 1)] for _ in range(n + 1)]
for u in range(n + 1):
  xu, yu = points[u]
  dist[u][u] = 0
  for v in range(u + 1, n + 1):
    xv, yv = points[v]
    dist[u][v] = dist[v][u] = math.sqrt((xv - xu) ** 2 + (yv - yu) ** 2)

tours = [[INF for _ in range(n + 1)] for _ in range(1 << (n + 1))]
tours[0][n] = 0.0
for mask in range(1 << (n + 1)):
  c = sum([(mask >> u) & 1 for u in range(n)])
  if c > k:
  	continue

  for cur in range(n + 1):
    for nxt in range(n + 1):
      if (mask >> nxt) & 1 != 0:
        continue
      visited = mask | (1 << nxt)
      if c < k or (c == k and nxt == n):
        tours[visited][nxt] = min(tours[visited][nxt], tours[mask][cur] + dist[cur][nxt])

dp = [INF for _ in range(1 << n)]
dp[0] = 0.0
for mask in range(1, 1 << n):
  subset = mask
  while subset > 0:
    subset = (subset - 1) & mask
    dp[mask] = min(dp[mask], dp[subset] + tours[(1 << n) | (mask - subset)][n])

print(dp[-1])