import itertools



n = int(eval(input())) 

p_list = itertools.permutations([x for x in range(n)])



# for p in p_list:

#     print(p)



a_list = []

for i in range(n):

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





d_sum = 0

cnt = 0

for p in p_list:

    cnt+=1

    curr_d_sum = 0

    curr_pos = p[0]

    for i in p:

        x_d = a_list[curr_pos][0] - a_list[i][0]

        y_d = a_list[curr_pos][1] - a_list[i][1]

        d = (x_d**2 + y_d**2)**0.5

        curr_d_sum += d

        curr_pos = i

    d_sum += curr_d_sum

print((d_sum/cnt))
from itertools import permutations

from math import sqrt



n = int(eval(input()))

xyl = []

for _ in range(n):

    x,y = list(map(int, input().split()))

    xyl.append((x,y))



ll = list(range(0,n))

perml = list(permutations(ll, n))



val = 0

for perm in perml:

    prev_x = 0

    prev_y = 0

    for i,p in enumerate(perm):

        x,y = xyl[p]

        if i == 0:

            prev_x = x

            prev_y = y

        else:

            val += sqrt( (prev_x-x)**2 + (prev_y-y)**2 )

            prev_x = x

            prev_y = y

    

ans = val/len(perml)

print(ans)
import itertools

n = int(eval(input()))
p_list = itertools.permutations([x for x in range(n)])
# for p in p_list:
#     print(p)
a_list = []
for i in range(n):
    a_list.append(list(map(int, input().split())))
d_sum = 0
cnt = 0
for p in p_list:
    cnt += 1
    curr_d_sum = 0
    curr_pos = p[0]
    for i in p:
        x_d = a_list[curr_pos][0] - a_list[i][0]
        y_d = a_list[curr_pos][1] - a_list[i][1]
        d = (x_d**2 + y_d**2) ** 0.5
        curr_d_sum += d
        curr_pos = i
    d_sum += curr_d_sum
print((d_sum / cnt))

from itertools import permutations
from math import sqrt

n = int(eval(input()))
xyl = []
for _ in range(n):
    x, y = list(map(int, input().split()))
    xyl.append((x, y))
ll = list(range(0, n))
perml = list(permutations(ll, n))
val = 0
for perm in perml:
    prev_x = 0
    prev_y = 0
    for i, p in enumerate(perm):
        x, y = xyl[p]
        if i == 0:
            prev_x = x
            prev_y = y
        else:
            val += sqrt((prev_x - x) ** 2 + (prev_y - y) ** 2)
            prev_x = x
            prev_y = y
ans = val / len(perml)
print(ans)

-import itertools +from itertools import permutations +from math import sqrt -p_list = itertools.permutations([x for x in range(n)]) -# for p in p_list: -#     print(p) -a_list = [] -for i in range(n): -    a_list.append(list(map(int, input().split()))) -d_sum = 0 -cnt = 0 -for p in p_list: -    cnt += 1 -    curr_d_sum = 0 -    curr_pos = p[0] -    for i in p: -        x_d = a_list[curr_pos][0] - a_list[i][0] -        y_d = a_list[curr_pos][1] - a_list[i][1] -        d = (x_d**2 + y_d**2) ** 0.5 -        curr_d_sum += d -        curr_pos = i -    d_sum += curr_d_sum -print((d_sum / cnt)) +xyl = [] +for _ in range(n): +    x, y = list(map(int, input().split())) +    xyl.append((x, y)) +ll = list(range(0, n)) +perml = list(permutations(ll, n)) +val = 0 +for perm in perml: +    prev_x = 0 +    prev_y = 0 +    for i, p in enumerate(perm): +        x, y = xyl[p] +        if i == 0: +            prev_x = x +            prev_y = y +        else: +            val += sqrt((prev_x - x) ** 2 + (prev_y - y) ** 2) +            prev_x = x +            prev_y = y +ans = val / len(perml) +print(ans)