#include <iostream>
#include <vector>
using namespace std;
typedef long long ll;

const ll MOD = 1e9 + 7;
ll solve(const vector<int>& dames){
	const int n = dames.size();

	vector<int> cnt(n, 0);
	for(int d : dames){
		++cnt[d];
	}

	vector<ll> dp(n + 1, 0);
	dp[0] = 1;

	for(int c : cnt){
		for(int s=n-1;s>=0;s--){
			dp[s+1] = (dp[s+1] + dp[s] * c % MOD) % MOD;
		}
	}

	vector<ll> perms(n + 1);
	perms[0] = 1;
	for(int i=1;i<=n;i++)perms[i] = perms[i-1] * i % MOD;

	ll res = 0;
	for(int i=0;i<=n;i++){
		ll tmp = dp[i] * perms[n-i] % MOD;
		if(i % 2 == 0) {
			res = (res + tmp) % MOD; 
		} else {
			res = (res - tmp + MOD) % MOD;
		}
	}

	return res;
}

int main(){
	int N;
	cin >> N;

	vector<int> dames(N);
	for(int i=0;i<N;i++)cin >> dames[i];

	cout << solve(dames) << endl;
	return 0;
}