MOD = 10**9 + 7

N = int(input())
A = [int(input().strip()) for _ in range(N)]

cnt = [0] * 5000
for a in A:
    cnt[a] += 1

xs = [x for x in range(5000) if cnt[x] > 0]
m = len(xs)

dp = [0] * (m + 1)
dp[0] = 1
current_max = 0

for x in xs:
    c = cnt[x]
    for k in range(current_max, -1, -1):
        if dp[k] > 0:
            if k + 1 <= m:
                dp[k + 1] = (dp[k + 1] + dp[k] * c) % MOD
    current_max += 1

fact = [1] * (N + 1)
for i in range(1, N + 1):
    fact[i] = fact[i - 1] * i % MOD

ans = 0
for k in range(0, m + 1):
    if k > N:
        continue
    sign = (-1) ** k
    term = sign * dp[k] * fact[N - k]
    term %= MOD
    ans = (ans + term) % MOD

print(ans % MOD)