#include<bits/stdc++.h>
#include<atcoder/modint>
using namespace std;
using namespace atcoder;
using mint = modint1000000007;

void solve(){
	int n;
	cin >> n;
	map<int, int> cnt;
	int a;
	for(int i = 0; i < n; i++){
		cin >> a;
		if(a < n) cnt[a]++;
	}
	vector<mint> dp(n + 1, 0);
	dp[0] = 1;
	for(auto tmp:cnt){
		int v = tmp.second;
		for(int i = n; i > 0; i--) dp[i] += dp[i - 1] * v;
	}
	vector<mint> fact(n + 1);
	fact[0] = 1;
	for(int i = 1; i <= n; i++) fact[i] = fact[i - 1] * i;
	
	mint ans = 0;
	mint pm = 1;
	for(int i = 0; i <= n; i++){
		ans += pm * dp[i] * fact[n - i];
		pm *= -1;
	}
	cout << ans.val() << "\n";

}

int main(){
    cin.tie(0)->sync_with_stdio(0);
    int t;
    t = 1;
    // cin >> t;
    while(t--) solve();
}