def n_n(n):

  c = 1

  for i in range(1,n+1):

    c = c * i

  return c

import itertools as itr

N = int(eval(input()))

n = n_n(N)



rr=[]

xy = [[0,0]] * (N)

for i in range(N):

  xy[i] = list(map(int,input().split()))

  

all = list(itr.permutations(xy))

for line in all:

  r = [0] * (N+1)

  x = [0]*(N+1)

  y = [0]*(N+1)

  for i in range(N-1):

    x[i+1] = line[i+1][0] - line[i][0]

    y[i+1] = line[i+1][1] - line[i][1]

    r[i+1] = (x[i+1]**2 + y[i+1]**2)**(1/2)

  rr.append(sum(i for i in r))

print((sum(i for i in rr)/n))
import itertools as itr

n = int(eval(input()))

xy = []

for i in range(n):

    x, y = list(map(int, input().split(" ")))

    xy.append([x, y])

all = list(itr.permutations(xy))

n_n = 1

ans = []

for i in range(2,n+1):

    n_n = n_n*i

for line in all:

    r = [0] * (n+1)

    x = [0]*(n+1)

    y = [0]*(n+1)

    for i in range(n-1):

        x[i+1] = line[i+1][0] - line[i][0]

        y[i+1] = line[i+1][1] - line[i][1]

        r[i+1] = (x[i+1]**2 + y[i+1]**2)**(1/2)

    ans.append(sum(r))

print((sum(ans)/n_n))

def n_n(n):
    c = 1
    for i in range(1, n + 1):
        c = c * i
    return c


import itertools as itr

N = int(eval(input()))
n = n_n(N)
rr = []
xy = [[0, 0]] * (N)
for i in range(N):
    xy[i] = list(map(int, input().split()))
all = list(itr.permutations(xy))
for line in all:
    r = [0] * (N + 1)
    x = [0] * (N + 1)
    y = [0] * (N + 1)
    for i in range(N - 1):
        x[i + 1] = line[i + 1][0] - line[i][0]
        y[i + 1] = line[i + 1][1] - line[i][1]
        r[i + 1] = (x[i + 1] ** 2 + y[i + 1] ** 2) ** (1 / 2)
    rr.append(sum(i for i in r))
print((sum(i for i in rr) / n))

import itertools as itr

n = int(eval(input()))
xy = []
for i in range(n):
    x, y = list(map(int, input().split(" ")))
    xy.append([x, y])
all = list(itr.permutations(xy))
n_n = 1
ans = []
for i in range(2, n + 1):
    n_n = n_n * i
for line in all:
    r = [0] * (n + 1)
    x = [0] * (n + 1)
    y = [0] * (n + 1)
    for i in range(n - 1):
        x[i + 1] = line[i + 1][0] - line[i][0]
        y[i + 1] = line[i + 1][1] - line[i][1]
        r[i + 1] = (x[i + 1] ** 2 + y[i + 1] ** 2) ** (1 / 2)
    ans.append(sum(r))
print((sum(ans) / n_n))

-def n_n(n): -    c = 1 -    for i in range(1, n + 1): -        c = c * i -    return c - - -N = int(eval(input())) -n = n_n(N) -rr = [] -xy = [[0, 0]] * (N) -for i in range(N): -    xy[i] = list(map(int, input().split())) +n = int(eval(input())) +xy = [] +for i in range(n): +    x, y = list(map(int, input().split(" "))) +    xy.append([x, y]) +n_n = 1 +ans = [] +for i in range(2, n + 1): +    n_n = n_n * i -    r = [0] * (N + 1) -    x = [0] * (N + 1) -    y = [0] * (N + 1) -    for i in range(N - 1): +    r = [0] * (n + 1) +    x = [0] * (n + 1) +    y = [0] * (n + 1) +    for i in range(n - 1): -    rr.append(sum(i for i in r)) -print((sum(i for i in rr) / n)) +    ans.append(sum(r)) +print((sum(ans) / n_n))