from _collections import defaultdict
n=int(input())
a=list(map(int,input().split()))
kai=[1]*22
for i in range(1,21):
    kai[i]=kai[i-1]*i

ans=1
cnt=defaultdict(int)
for x in a:
    cnt[x]+=1
for x in cnt:
    ans*=kai[cnt[x]]
print(kai[n]//ans)