N = int(eval(input()))

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

s = 0

def perm(ns):

    acc = []

    def fill(ms, remains):

        if remains:

            for m in remains:

                fill(ms + [m], [x for x in remains if x != m])

        else:

            acc.append(ms)

    fill([], ns)

    return acc



s = 0

for indexes in perm(list(range(N))):

    xys = [XYS[i] for i in indexes]

    x0, y0 = xys[0]

    for x1, y1 in xys:

        s += ((x0 - x1)**2 + (y0 - y1)**2) ** 0.5

        x0 = x1

        y0 = y1



nf = 1

for i in range(1, N+1):

    nf *= i

ans = s / nf



print(ans)
from itertools import permutations as perm



N = int(eval(input()))

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

s = 0

for indexes in perm(list(range(N))):

    xys = [XYS[i] for i in indexes]

    x0, y0 = xys[0]

    for x1, y1 in xys:

        s += ((x0 - x1)**2 + (y0 - y1)**2) ** 0.5

        x0 = x1

        y0 = y1



nf = 1

for i in range(1, N+1):

    nf *= i

ans = s / nf



print(ans)
N = int(eval(input()))
XYS = [list(map(int, input().split())) for _ in range(N)]
s = 0


def perm(ns):
    acc = []

    def fill(ms, remains):
        if remains:
            for m in remains:
                fill(ms + [m], [x for x in remains if x != m])
        else:
            acc.append(ms)

    fill([], ns)
    return acc


s = 0
for indexes in perm(list(range(N))):
    xys = [XYS[i] for i in indexes]
    x0, y0 = xys[0]
    for x1, y1 in xys:
        s += ((x0 - x1) ** 2 + (y0 - y1) ** 2) ** 0.5
        x0 = x1
        y0 = y1
nf = 1
for i in range(1, N + 1):
    nf *= i
ans = s / nf
print(ans)

from itertools import permutations as perm

N = int(eval(input()))
XYS = [list(map(int, input().split())) for _ in range(N)]
s = 0
for indexes in perm(list(range(N))):
    xys = [XYS[i] for i in indexes]
    x0, y0 = xys[0]
    for x1, y1 in xys:
        s += ((x0 - x1) ** 2 + (y0 - y1) ** 2) ** 0.5
        x0 = x1
        y0 = y1
nf = 1
for i in range(1, N + 1):
    nf *= i
ans = s / nf
print(ans)

+from itertools import permutations as perm + -s = 0 - - -def perm(ns): -    acc = [] - -    def fill(ms, remains): -        if remains: -            for m in remains: -                fill(ms + [m], [x for x in remains if x != m]) -        else: -            acc.append(ms) - -    fill([], ns) -    return acc - -