import sys

input = lambda: sys.stdin.readline().rstrip()

from itertools import combinations_with_replacement as cwr , combinations , permutations ,product

from math import sqrt

a=[]

for _ in range(int(eval(input()))):

    a.append([int(i) for i in input().split()])

p=list(permutations(a))

ans=[]

for i in p:

    cur=0

    for j in range(len(i)-1):

        cur+=sqrt((i[j+1][0]-i[j][0])**2+(i[j+1][1]-i[j][1])**2)

    ans.append(cur)

print((sum(ans)/len(ans)))

    

import sys

input = lambda: sys.stdin.readline().rstrip()

from math import sqrt

a=[]

for _ in range(int(eval(input()))):

    a.append([int(i) for i in input().split()])

summ=0

for i in a:

    for j in a:

        summ+=sqrt((i[0]-j[0])**2+(i[1]-j[1])**2)

print((summ/len(a)))

        
import sys

input = lambda: sys.stdin.readline().rstrip()
from itertools import (
    combinations_with_replacement as cwr,
    combinations,
    permutations,
    product,
)
from math import sqrt

a = []
for _ in range(int(eval(input()))):
    a.append([int(i) for i in input().split()])
p = list(permutations(a))
ans = []
for i in p:
    cur = 0
    for j in range(len(i) - 1):
        cur += sqrt((i[j + 1][0] - i[j][0]) ** 2 + (i[j + 1][1] - i[j][1]) ** 2)
    ans.append(cur)
print((sum(ans) / len(ans)))

import sys

input = lambda: sys.stdin.readline().rstrip()
from math import sqrt

a = []
for _ in range(int(eval(input()))):
    a.append([int(i) for i in input().split()])
summ = 0
for i in a:
    for j in a:
        summ += sqrt((i[0] - j[0]) ** 2 + (i[1] - j[1]) ** 2)
print((summ / len(a)))

-from itertools import ( -    combinations_with_replacement as cwr, -    combinations, -    permutations, -    product, -) -p = list(permutations(a)) -ans = [] -for i in p: -    cur = 0 -    for j in range(len(i) - 1): -        cur += sqrt((i[j + 1][0] - i[j][0]) ** 2 + (i[j + 1][1] - i[j][1]) ** 2) -    ans.append(cur) -print((sum(ans) / len(ans))) +summ = 0 +for i in a: +    for j in a: +        summ += sqrt((i[0] - j[0]) ** 2 + (i[1] - j[1]) ** 2) +print((summ / len(a)))