MOD = 10**9 + 7

n = int(input())
A = [int(input()) for _ in range(n)]

from collections import defaultdict

cnt = defaultdict(int)
for a in A:
    cnt[a] += 1

# Initialize DP array for generating function coefficients
dp = [0] * (n + 1)
dp[0] = 1

for c in cnt.values():
    new_dp = [0] * (len(dp) + 1)
    for k in range(len(dp)):
        if dp[k] == 0:
            continue
        new_dp[k] = (new_dp[k] + dp[k]) % MOD  # Not taking this value
        if k + 1 < len(new_dp):
            new_dp[k + 1] = (new_dp[k + 1] + dp[k] * c) % MOD  # Taking this value
    dp = new_dp

# Precompute factorials modulo MOD
fact = [1] * (n + 1)
for i in range(1, n + 1):
    fact[i] = fact[i - 1] * i % MOD

result = 0
for k in range(len(dp)):
    if k > n:
        continue
    term = dp[k] * fact[n - k] % MOD
    if k % 2 == 1:
        term = (-term) % MOD
    result = (result + term) % MOD

print(result)