import itertools

n = int(eval(input()))

point = []

for i in range(n):

  a,b = list(map(float,input().split()))

  point.append((a,b))

ans = 0.0

div = 0

for pm in itertools.permutations(point):

  div += 1

  for j in range(n-1):

    ans += ((pm[j][0]-pm[j+1][0])**2 + (pm[j][1]-pm[j+1][1])**2) ** 0.5

print((ans / div))
from itertools import permutations

from math import factorial

n = int(eval(input()))

town = [complex(*list(map(int,input().split()))) for _ in range(n)]

d = 0

for l in permutations(town):

  for i in range(n-1):

    d += abs(l[i]-l[i+1])

print((d/factorial(n)))
import itertools

n = int(eval(input()))
point = []
for i in range(n):
    a, b = list(map(float, input().split()))
    point.append((a, b))
ans = 0.0
div = 0
for pm in itertools.permutations(point):
    div += 1
    for j in range(n - 1):
        ans += ((pm[j][0] - pm[j + 1][0]) ** 2 + (pm[j][1] - pm[j + 1][1]) ** 2) ** 0.5
print((ans / div))

from itertools import permutations
from math import factorial

n = int(eval(input()))
town = [complex(*list(map(int, input().split()))) for _ in range(n)]
d = 0
for l in permutations(town):
    for i in range(n - 1):
        d += abs(l[i] - l[i + 1])
print((d / factorial(n)))

-import itertools +from itertools import permutations +from math import factorial -point = [] -for i in range(n): -    a, b = list(map(float, input().split())) -    point.append((a, b)) -ans = 0.0 -div = 0 -for pm in itertools.permutations(point): -    div += 1 -    for j in range(n - 1): -        ans += ((pm[j][0] - pm[j + 1][0]) ** 2 + (pm[j][1] - pm[j + 1][1]) ** 2) ** 0.5 -print((ans / div)) +town = [complex(*list(map(int, input().split()))) for _ in range(n)] +d = 0 +for l in permutations(town): +    for i in range(n - 1): +        d += abs(l[i] - l[i + 1]) +print((d / factorial(n)))