#include<iostream>
#include<cstdio>
#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<cctype>
#include<cstdlib>
#include<algorithm>
#include<bitset>
#include<vector>
#include<list>
#include<deque>
#include<queue>
#include<map>
#include<set>
#include<stack>
#include<cmath>
#include<sstream>
#include<fstream>
#include<iomanip>
#include<ctime>
#include<complex>
#include<functional>
#include<climits>
#include<cassert>
#include<iterator>
#include<unordered_map>
using namespace std;
#define MOD 1000000007
#define MAX 5003
long long int cnt[MAX];
int n;
vector<long long int> v;
vector<long long int> cn;
long long int dp[MAX][MAX];
long long int k[MAX];
int main(){
	scanf("%d", &n);
	k[0] = 1LL;
	for (int i = 1; i < MAX; i++){
		k[i] = k[i - 1];
		k[i] *= (long long int)(i);
		k[i] %= MOD;
	}
	for (int i = 0; i < n; i++){
		int a;
		scanf("%d", &a);
		cnt[a]++;
	}
	for (int i = 0; i < MAX; i++){
		if (cnt[i]){
			v.push_back(i);
			cn.push_back(cnt[i]);
		}
	}
	dp[0][0] = 1LL;
	for (int i = 0; i < v.size(); i++){
		for (int j = 0; j <= i; j++){
			dp[i + 1][j+1] += dp[i][j]*cn[i];
			dp[i + 1][j] += dp[i][j];
			dp[i + 1][j + 1] %= MOD;
			dp[i + 1][j] %= MOD;
		}
	}
	long long int ans = 0;
	for (int i = 0; i <= v.size(); i++){
		long long int g = 1LL;
		if (i % 2 == 1LL){
			g = -1LL;
		}
		long long int way = dp[v.size()][i] * k[n - i];
		way %= MOD;
		way *= g;
		while (way < 0){
			way += MOD;
		}
		ans += way;
		ans %= MOD;
	}
	if (ans < 0){
		return 1;
	}
	printf("%lld\n", ans);
	return 0;
	return 0;
}