import itertools

n = int(eval(input()))

xy = []

for i in range(n):

    xy.append(list(map(int, input().split())))

per = list(itertools.permutations([i for i in range(n)]))

dist = 0

for i in per:

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

        xi = xy[i[j]][0]

        yi = xy[i[j]][1]

        xj = xy[i[j+1]][0]

        yj = xy[i[j+1]][1]

        dist += ((xi - xj) ** 2 + (yi - yj) ** 2) ** 0.5

dist /= len(per)

print(dist)
import itertools

N = int(eval(input()))

x = []

y = []

for i in range(N):

    xy = list(map(int, input().split()))

    x.append(xy[0])

    y.append(xy[1])





l = [i for i in range(N)]

ans = 0

cnt = 0

for i in itertools.permutations(l, N):

    cnt += 1

    for j in range(1, N):

        x1 = x[i[j]]

        x2 = x[i[j-1]]

        y1 = y[i[j]]

        y2 = y[i[j-1]]

        ans += pow((x1 - x2)**2 + (y1 - y2)**2, 0.5)

        # print(i, j, x1, y1, x2, y2)

ans /= cnt

print(ans)
import itertools

n = int(eval(input()))
xy = []
for i in range(n):
    xy.append(list(map(int, input().split())))
per = list(itertools.permutations([i for i in range(n)]))
dist = 0
for i in per:
    for j in range(len(i) - 1):
        xi = xy[i[j]][0]
        yi = xy[i[j]][1]
        xj = xy[i[j + 1]][0]
        yj = xy[i[j + 1]][1]
        dist += ((xi - xj) ** 2 + (yi - yj) ** 2) ** 0.5
dist /= len(per)
print(dist)

import itertools

N = int(eval(input()))
x = []
y = []
for i in range(N):
    xy = list(map(int, input().split()))
    x.append(xy[0])
    y.append(xy[1])
l = [i for i in range(N)]
ans = 0
cnt = 0
for i in itertools.permutations(l, N):
    cnt += 1
    for j in range(1, N):
        x1 = x[i[j]]
        x2 = x[i[j - 1]]
        y1 = y[i[j]]
        y2 = y[i[j - 1]]
        ans += pow((x1 - x2) ** 2 + (y1 - y2) ** 2, 0.5)
        # print(i, j, x1, y1, x2, y2)
ans /= cnt
print(ans)

-n = int(eval(input())) -xy = [] -for i in range(n): -    xy.append(list(map(int, input().split()))) -per = list(itertools.permutations([i for i in range(n)])) -dist = 0 -for i in per: -    for j in range(len(i) - 1): -        xi = xy[i[j]][0] -        yi = xy[i[j]][1] -        xj = xy[i[j + 1]][0] -        yj = xy[i[j + 1]][1] -        dist += ((xi - xj) ** 2 + (yi - yj) ** 2) ** 0.5 -dist /= len(per) -print(dist) +N = int(eval(input())) +x = [] +y = [] +for i in range(N): +    xy = list(map(int, input().split())) +    x.append(xy[0]) +    y.append(xy[1]) +l = [i for i in range(N)] +ans = 0 +cnt = 0 +for i in itertools.permutations(l, N): +    cnt += 1 +    for j in range(1, N): +        x1 = x[i[j]] +        x2 = x[i[j - 1]] +        y1 = y[i[j]] +        y2 = y[i[j - 1]] +        ans += pow((x1 - x2) ** 2 + (y1 - y2) ** 2, 0.5) +        # print(i, j, x1, y1, x2, y2) +ans /= cnt +print(ans)