#include <stdio.h>

const long long mod = 1000000007;

int main()
{
	int N,C[5050] = {0,};
	long long D[5050] = {1,};
	
	scanf ("%d",&N);
	for (int i=0;i<N;i++){
		int x; scanf ("%d",&x);
		C[x]++;
	}

	for (int k=0,c=0;k<N;k++) if (C[k]){
		for (int i=c;i>=0;i--){
			D[i+1] = (D[i+1] + mod - D[i] * C[k] % mod) % mod;
		}
		c++;
	}

	long long ans = 0, fact = 1;
	for (int i=N;i>=0;i--){
		ans = (ans + D[i] * fact) % mod;
		fact = fact * (N - i + 1) % mod;
	}

	printf ("%lld\n",ans);

	return 0;
}