#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint1000000007;
using namespace std;
#define rep(i,n) for(int i=0;i<(n);i++)
#define Inf 1000000001


int main(){
	
	int n;
	cin>>n;
	
	vector<int> cnt(5000,0);
	rep(i,n){
		int a;
		cin>>a;
		cnt[a] ++;
	}
	
	vector<mint> dp(n+1,0);
	dp[0] = 1;
	
	rep(i,5000){
		if(cnt[i]==0)continue;
		vector<mint> ndp(n+1,0);
		rep(j,dp.size()){
			if(dp[j]==0)continue;
			ndp[j] += dp[j];
			if(i<n && j+1<dp.size()){
				ndp[j+1] += dp[j] * cnt[i];
			}
		}
		swap(dp,ndp);
	}
	mint c = 1;
	rep(i,n+1){
		dp[n-i] *= c;
		c *= i+1;
	}
	mint ans = 0;
	rep(i,n+1){
		if(i%2 == 0)ans += dp[i];
		else ans -= dp[i];
	}
	cout<<ans.val()<<endl;
	return 0;
}