import copy
from functools import lru_cache
import sys
sys.setrecursionlimit(1000000)

N = int(input())
A = list(map(int,input().split()))

B = [min(A[i],3) for i in range(N)]
B = tuple(B)
print(B)

@lru_cache(maxsize=None)
def solve(X):
    ret = 1
    Z = list(X)
    loop = N
    for i,v in enumerate(Z):
        if v < 3:
            T = copy.copy(Z)
            T[i] = v+1
            T = tuple(T)
            ret += solve(T)/N
        else:
            loop -= 1
    if loop == 0:
        ret = 0
    else:
        ret *= N/loop
    #print(Z,ret)
    return ret

ans = solve(B)
print(ans)