import itertools

import math



N = int(eval(input()))

xy  = [[int(i) for i in input().split()] for j in range(N)]

distance = [[0 for j in range(N)] for i in range(N)]

for i in range(N):

    for j in range(N):

        xi = xy[i][0]

        yi = xy[i][1]

        xj = xy[j][0]

        yj = xy[j][1]

        d = math.sqrt((xi-xj)**2+(yi-yj)**2)

        distance[i][j] = d

        distance[j][i] = d



anslist=[]

for route in itertools.permutations(list(range(N)),N):

    total=0

    for i in range(N-1):

        start = route[i]

        goal = route[j]

        total += distance[start][goal]

    anslist.append(total)



print((sum(anslist)/len(anslist)))
import itertools

import math



N = int(eval(input()))

xy  = [[int(i) for i in input().split()] for j in range(N)]

distance = [[0 for j in range(N)] for i in range(N)]

for i in range(N):

    for j in range(N):

        xi = xy[i][0]

        yi = xy[i][1]

        xj = xy[j][0]

        yj = xy[j][1]

        d = math.sqrt((xi-xj)**2+(yi-yj)**2)

        distance[i][j] = d

        distance[j][i] = d



print((sum([sum(i) for i in distance])/N))

import itertools
import math

N = int(eval(input()))
xy = [[int(i) for i in input().split()] for j in range(N)]
distance = [[0 for j in range(N)] for i in range(N)]
for i in range(N):
    for j in range(N):
        xi = xy[i][0]
        yi = xy[i][1]
        xj = xy[j][0]
        yj = xy[j][1]
        d = math.sqrt((xi - xj) ** 2 + (yi - yj) ** 2)
        distance[i][j] = d
        distance[j][i] = d
anslist = []
for route in itertools.permutations(list(range(N)), N):
    total = 0
    for i in range(N - 1):
        start = route[i]
        goal = route[j]
        total += distance[start][goal]
    anslist.append(total)
print((sum(anslist) / len(anslist)))

import itertools
import math

N = int(eval(input()))
xy = [[int(i) for i in input().split()] for j in range(N)]
distance = [[0 for j in range(N)] for i in range(N)]
for i in range(N):
    for j in range(N):
        xi = xy[i][0]
        yi = xy[i][1]
        xj = xy[j][0]
        yj = xy[j][1]
        d = math.sqrt((xi - xj) ** 2 + (yi - yj) ** 2)
        distance[i][j] = d
        distance[j][i] = d
print((sum([sum(i) for i in distance]) / N))

-anslist = [] -for route in itertools.permutations(list(range(N)), N): -    total = 0 -    for i in range(N - 1): -        start = route[i] -        goal = route[j] -        total += distance[start][goal] -    anslist.append(total) -print((sum(anslist) / len(anslist))) +print((sum([sum(i) for i in distance]) / N))