// yukicoder: No.243 出席番号(2)
// 2019.7.18 bal4u

#include <stdio.h>

typedef long long ll;

#if 1
#define gc() getchar_unlocked()
#else
#define gc() getchar()
#endif

int in() {   // 非負整数の入力
	int n = 0, c = gc();
	do n = 10 * n + (c & 0xf); while ((c = gc()) >= '0');
	return n;
}

#define MOD 1000000007
#define MAX 5003
int fact[MAX] = {1,1};
int f[MAX]; int N;
int dp[MAX];

 int main()
{
	int i, j, k;
	ll ans;
	
	N = in(); for (i = 0; i < N; i++) f[in()]++;
	for (i = 2; i <= N; i++) fact[i] = (ll)fact[i-1]*i % MOD;	
	
	dp[0] = 1;
	for (i = 0; i < N; i++) if (f[i]) for (j = i; j >= 0; j--) {
		dp[j+1] = (dp[j+1] + (ll)f[i]*dp[j]) % MOD;
	}
	
	ans = 0, k = 1; for (i = 0; i <= N; i++) {
		int t = (ll)dp[i] * fact[N-i] % MOD;
		if (k) ans += t; else ans -= t;
		k = 1-k;
	}
	ans %= MOD; if (ans < 0) ans += MOD;
	printf("%d\n", (int)ans);
	return 0;
}