#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define M 1000000007
ll n,dp[2][5005],c[5005],k[5005],ans;
int main(void){
    cin>>n;
    k[0]=1;
    for(ll i=1;i<=n;i++)k[i]=k[i-1]*i%M;
    for(int i=0;i<n;i++){
		ll a;
		cin>>a;
		c[a]++;
	}
	dp[0][1]=c[0];
	for(int i=1,l=0;i<n;i++,l++){
		dp[l%2][0]=1;
		for(int j=1;j<=i+1;j++){
			dp[i%2][j]=(dp[l%2][j]+dp[l%2][j-1]*c[i])%M;
		}
	}
	ans=k[n];
	for(int i=1;i<=n;i++){
		if(i%2)ans=(ans+M-dp[(n-1)%2][i]*k[n-i]%M)%M;
		else ans=(ans+dp[(n-1)%2][i]*k[n-i])%M;
	}
	cout<<ans<<endl;
}