MOD = 10**9 + 7

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

from collections import defaultdict

# Count the occurrences of each disliked number
cnt = defaultdict(int)
for a in A:
    cnt[a] += 1

# DP to compute C_k: number of ways to choose k elements with all distinct A_i
dp = [0] * (N + 1)
dp[0] = 1

for v in cnt:
    c = cnt[v]
    # Iterate backwards to avoid overwriting the values we need to use
    for j in range(N, -1, -1):
        if dp[j]:
            if j + 1 <= N:
                dp[j + 1] = (dp[j + 1] + dp[j] * c) % MOD

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

# Calculate the answer using inclusion-exclusion principle
ans = 0
for k in range(0, N + 1):
    term = pow(-1, k, MOD) * dp[k] % MOD
    term = term * fact[N - k] % MOD
    ans = (ans + term) % MOD

print(ans % MOD)