import sys,random,bisect
from collections import deque,defaultdict
from heapq import heapify,heappop,heappush
from itertools import cycle, permutations
from math import log,gcd

input = lambda :sys.stdin.readline().rstrip()
mi = lambda :map(int,input().split())
li = lambda :list(mi())

N = int(input())
A = li()

cnt = [0] * (N+1)
g1 = [1] * (N+1)
for i in range(1,N+1):
    g1[i] = i * g1[i-1]

for a in A:
    cnt[a] += 1

res = g1[N]
for i in range(1,N+1):
    res //= g1[cnt[i]]

print(res)