import itertools



n = int(eval(input()))

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



city_number = [i for i in range(n)]

permutations_city_number = itertools.permutations(city_number)



sum_distance = 0

cnt = 0



for city in permutations_city_number:

    memo = 0

    for x in city:

        if memo == 0:

            city1 = x

            memo = 1

        sum_distance += ((city_distance[city1][0] - city_distance[x][0]) ** 2 + (city_distance[city1][1] - city_distance[x][1]) ** 2) ** 0.5

    cnt += 1



print((sum_distance/cnt))
import itertools



n = int(eval(input()))

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



s = [i for i in range(n)]



path = list(itertools.permutations(s, len(s)))



ans = 0



for i in range(len(path)):

    for j in range(n-1):

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

        

print((ans/len(path)))

import itertools

n = int(eval(input()))
city_distance = [list(map(int, input().split())) for _ in range(n)]
city_number = [i for i in range(n)]
permutations_city_number = itertools.permutations(city_number)
sum_distance = 0
cnt = 0
for city in permutations_city_number:
    memo = 0
    for x in city:
        if memo == 0:
            city1 = x
            memo = 1
        sum_distance += (
            (city_distance[city1][0] - city_distance[x][0]) ** 2
            + (city_distance[city1][1] - city_distance[x][1]) ** 2
        ) ** 0.5
    cnt += 1
print((sum_distance / cnt))

import itertools

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

-city_distance = [list(map(int, input().split())) for _ in range(n)] -city_number = [i for i in range(n)] -permutations_city_number = itertools.permutations(city_number) -sum_distance = 0 -cnt = 0 -for city in permutations_city_number: -    memo = 0 -    for x in city: -        if memo == 0: -            city1 = x -            memo = 1 -        sum_distance += ( -            (city_distance[city1][0] - city_distance[x][0]) ** 2 -            + (city_distance[city1][1] - city_distance[x][1]) ** 2 +li = [list(map(int, input().split())) for _ in range(n)] +s = [i for i in range(n)] +path = list(itertools.permutations(s, len(s))) +ans = 0 +for i in range(len(path)): +    for j in range(n - 1): +        ans += ( +            (li[path[i][j]][0] - li[path[i][j + 1]][0]) ** 2 +            + (li[path[i][j]][1] - li[path[i][j + 1]][1]) ** 2 -    cnt += 1 -print((sum_distance / cnt)) +print((ans / len(path)))