#include <iostream>
#include <vector>
using ll = long long;
constexpr ll MOD = 1000000007;
int main()
{
    int N;
    std::cin >> N;
    std::vector<int> dislike(N, 0);
    for (int i = 0, A; i < N; i++) { std::cin >> A, dislike[A]++; }
    std::vector<ll> dp(N + 1, 0);
    dp[0] = 1;
    for (int i = 0; i < N; i++) {
        for (int j = N - 1; j >= 0; j--) { (dp[j + 1] += dp[j] * dislike[i]) %= MOD; }
    }
    ll f = 1, ans = 0;
    for (int i = 0; i <= N; i++) {
        const ll S = dp[N - i] * f % MOD;
        (ans += ((N - i) % 2 == 0 ? S : MOD - S)) %= MOD, (f *= (i + 1)) %= MOD;
    }
    std::cout << ans << std::endl;
    return 0;
}