N = int(input())
A = list(map(int, input().split()))
D = [0] * 25
fact = [1] * (N + 1)
for i in range(1, N + 1):
    fact[i] = fact[i - 1] * i
    
for a in A:
    D[a] += 1
    
ans = fact[N]
for i in range(25):
    ans //= fact[D[i]]
print(ans)