import itertools

N = int(eval(input()))

xy = [list(map(int, input().split())) for _ in range(N)]



route = list(itertools.permutations(list(range(N))))



ans = 0

for i in range(len(route)):

  for j in range(N-1):

    a = route[i][j]

    b = route[i][j + 1]

    X = (xy[a][0] - xy[b][0]) ** 2

    Y = (xy[a][1] - xy[b][1]) ** 2

    ans += (X + Y) ** 0.5

print((ans / len(route))) 
import itertools

N = int(eval(input()))

xy = [list(map(int, input().split())) for _ in range(N)]



d = 0

c = 0

for x in itertools.permutations(xy):

  c += 1

  D = 0

  for i in range(N-1):

    D += ((x[i][0]-x[i+1][0]) ** 2 + (x[i][1]-x[i+1][1]) ** 2) ** 0.5

  d += D

ans = d / c

print(ans)
import itertools

N = int(eval(input()))
xy = [list(map(int, input().split())) for _ in range(N)]
route = list(itertools.permutations(list(range(N))))
ans = 0
for i in range(len(route)):
    for j in range(N - 1):
        a = route[i][j]
        b = route[i][j + 1]
        X = (xy[a][0] - xy[b][0]) ** 2
        Y = (xy[a][1] - xy[b][1]) ** 2
        ans += (X + Y) ** 0.5
print((ans / len(route)))

import itertools

N = int(eval(input()))
xy = [list(map(int, input().split())) for _ in range(N)]
d = 0
c = 0
for x in itertools.permutations(xy):
    c += 1
    D = 0
    for i in range(N - 1):
        D += ((x[i][0] - x[i + 1][0]) ** 2 + (x[i][1] - x[i + 1][1]) ** 2) ** 0.5
    d += D
ans = d / c
print(ans)

-route = list(itertools.permutations(list(range(N)))) -ans = 0 -for i in range(len(route)): -    for j in range(N - 1): -        a = route[i][j] -        b = route[i][j + 1] -        X = (xy[a][0] - xy[b][0]) ** 2 -        Y = (xy[a][1] - xy[b][1]) ** 2 -        ans += (X + Y) ** 0.5 -print((ans / len(route))) +d = 0 +c = 0 +for x in itertools.permutations(xy): +    c += 1 +    D = 0 +    for i in range(N - 1): +        D += ((x[i][0] - x[i + 1][0]) ** 2 + (x[i][1] - x[i + 1][1]) ** 2) ** 0.5 +    d += D +ans = d / c +print(ans)