import itertools

n=int(eval(input()))

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

p=list(itertools.permutations(list(range(n))))

ans=0

for i in p:

    for j in range(n-1):

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

print((ans/len(p)))
from itertools import permutations

n=int(eval(input()))

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

ans=0

p=list(permutations(list(range(n)),n))

for L in p:

    s=L[0]

    for i in L[1:]:

        ans+=((l[s][0]-l[i][0])**2+(l[s][1]-l[i][1])**2)**0.5

        s=i

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

n = int(eval(input()))
l = [list(map(int, input().split())) for _ in range(n)]
p = list(itertools.permutations(list(range(n))))
ans = 0
for i in p:
    for j in range(n - 1):
        ans += (
            (l[i[j + 1]][0] - l[i[j]][0]) ** 2 + (l[i[j + 1]][1] - l[i[j]][1]) ** 2
        ) ** 0.5
print((ans / len(p)))

from itertools import permutations

n = int(eval(input()))
l = [list(map(int, input().split())) for _ in range(n)]
ans = 0
p = list(permutations(list(range(n)), n))
for L in p:
    s = L[0]
    for i in L[1:]:
        ans += ((l[s][0] - l[i][0]) ** 2 + (l[s][1] - l[i][1]) ** 2) ** 0.5
        s = i
print((ans / len(p)))

-import itertools +from itertools import permutations -p = list(itertools.permutations(list(range(n)))) -for i in p: -    for j in range(n - 1): -        ans += ( -            (l[i[j + 1]][0] - l[i[j]][0]) ** 2 + (l[i[j + 1]][1] - l[i[j]][1]) ** 2 -        ) ** 0.5 +p = list(permutations(list(range(n)), n)) +for L in p: +    s = L[0] +    for i in L[1:]: +        ans += ((l[s][0] - l[i][0]) ** 2 + (l[s][1] - l[i][1]) ** 2) ** 0.5 +        s = i