from itertools import permutations

from math import factorial

n=int(eval(input()))

A=[list(map(int,input().split())) for i in range(n)]



cnt=0

for i in permutations(A,n):

    for j in range(1,n):

        cnt +=((i[j-1][0]-i[j][0])**2+(i[j-1][1]-i[j][1])**2)**0.5

print((cnt/factorial(n)))
from itertools import permutations

from math import factorial

n=int(eval(input()))

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



ans=0

for A in permutations(XY,n):

    cnt=0

    for j in range(n-1):

        cnt +=((A[j][0]-A[j+1][0])**2+(A[j][1]-A[j+1][1])**2)**0.5

    ans +=cnt

print((ans/factorial(n)))
from itertools import permutations
from math import factorial

n = int(eval(input()))
A = [list(map(int, input().split())) for i in range(n)]
cnt = 0
for i in permutations(A, n):
    for j in range(1, n):
        cnt += ((i[j - 1][0] - i[j][0]) ** 2 + (i[j - 1][1] - i[j][1]) ** 2) ** 0.5
print((cnt / factorial(n)))

from itertools import permutations
from math import factorial

n = int(eval(input()))
XY = [list(map(int, input().split())) for _ in range(n)]
ans = 0
for A in permutations(XY, n):
    cnt = 0
    for j in range(n - 1):
        cnt += ((A[j][0] - A[j + 1][0]) ** 2 + (A[j][1] - A[j + 1][1]) ** 2) ** 0.5
    ans += cnt
print((ans / factorial(n)))

-A = [list(map(int, input().split())) for i in range(n)] -cnt = 0 -for i in permutations(A, n): -    for j in range(1, n): -        cnt += ((i[j - 1][0] - i[j][0]) ** 2 + (i[j - 1][1] - i[j][1]) ** 2) ** 0.5 -print((cnt / factorial(n))) +XY = [list(map(int, input().split())) for _ in range(n)] +ans = 0 +for A in permutations(XY, n): +    cnt = 0 +    for j in range(n - 1): +        cnt += ((A[j][0] - A[j + 1][0]) ** 2 + (A[j][1] - A[j + 1][1]) ** 2) ** 0.5 +    ans += cnt +print((ans / factorial(n)))