import sys

# sys.setrecursionlimit(10 ** 9)  # Codeforcesでは350000程度に


def input():
    return sys.stdin.readline().strip()


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

A.sort()
ans = 1
for i in range(1, n + 1):
    ans *= i

B = [0] * 21
for i in range(n):
    B[A[i]] += 1

for i in range(21):
    for j in range(1, B[i] + 1):
        ans //= j

print(ans)