//Let's join Kaede Takagaki Fan Club !!
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
typedef long long ll;
typedef pair<int,int> P;
typedef pair<int,P> P1;
typedef pair<P,P> P2;
#define pu push
#define pb push_back
#define mp make_pair
#define eps 1e-7
#define INF 1000000000
#define fi first
#define sc second
#define rep(i,x) for(int i=0;i<x;i++)
#define repn(i,x) for(int i=1;i<=x;i++)
#define SORT(x) sort(x.begin(),x.end())
#define ERASE(x) x.erase(unique(x.begin(),x.end()),x.end())
#define POSL(x,v) (lower_bound(x.begin(),x.end(),v)-x.begin())
#define POSU(x,v) (upper_bound(x.begin(),x.end(),v)-x.begin())
#define all(x) x.begin(),x.end()
template<class T>
void dmp(T a){
	rep(i,a.size()) cout << a[i] << " ";
	cout << endl;
}
template<class T>
bool chmax(T&a, T b){
	if(a < b){
		a = b;
		return 1;
	}
	return 0;
}
template<class T>
bool chmin(T&a, T b){
	if(a > b){
		a = b;
		return 1;
	}
	return 0;
}
template<class T>
void g(T &a){
	cin >> a;
}
template<class T>
void o(const T &a,bool space=false){
	cout << a << (space?' ':'\n');
}
//ios::sync_with_stdio(false);
const ll mod = 1000000007;//998244353
template<class T>
void add(T&a,T b){
	a+=b;
	if(a >= mod) a-=mod;
}

int n, a[5005];
ll dp[5005][5005], w[5005], F[5005];
int main(){
    F[0] = 1;
    repn(i, 5004) F[i] = F[i-1] * i % mod;
	cin >> n;
	repn(i, n) {
		cin >> a[i];
		w[a[i]]++;
	}
	dp[0][0] = 1;
	rep(j, n){
	    rep(i, j+1){
    		{
    			add(dp[j+1][i], dp[j][i]);
    			add(dp[j+1][i+1], dp[j][i] * w[j] % mod);
    		}
	    }
	}
	ll ans = 0;
	rep(j, n+1) {
	    if(j%2 == 0) ans += dp[n][j] * F[n-j] % mod;
	    else ans -= dp[n][j] * F[n-j] % mod;
	}
	printf("%lld\n", (ans%mod+mod)%mod);
}