#include <bits/stdc++.h>
#define rep(i, a) rep2 (i, 0, a)
#define rep2(i, a, b) for (int i = (a); i < (b); i++)
#define repr(i, a) repr2 (i, 0, a)
#define repr2(i, a, b) for (int i = (b) - 1; i >= (a); i--)
#define chmin(a, b) ((b) < a && (a = (b), true))
#define chmax(a, b) (a < (b) && (a = (b), true))
#define rng(a) (a).begin(), (a).end()
using namespace std;
typedef long long ll;

const ll mod = 1e9 + 7;
ll dp[5050][5050];
ll fact[5050];

int main() {
	int N;
	cin >> N;
	vector<int> a(N);
	rep (i, N) {
		int A;
		cin >> A;
		a[A]++;
	}
	fact[0] = 1;
	rep2 (i, 1, 5050) fact[i] = (fact[i - 1] * i) % mod;
	dp[0][0] = 1;
	dp[0][1] = a[0];
	rep2 (i, 1, N) rep (j, i + 2) {
		if (j == 0) dp[i][j] = 1;
		else {
			dp[i][j] = (dp[i - 1][j] + dp[i - 1][j - 1] * a[i]) % mod;
		}
	}
	ll ans = 0;
	rep2 (i, 1, N + 1) {
		ll sign = i & 1 ? 1 : -1;
		ans += sign * dp[N - 1][i] * fact[N - i] % mod;
	}
	ans = (fact[N] - ans) % mod;
	ans += mod; ans %= mod;
	cout << ans << endl;
	return 0;
}