#include <bits/stdc++.h>
#define lint __int128
#define int long long
#define Il inline
#define fi first
#define se second
#define vec vector
#define pb push_back
#define IT ::iterator
#define p_q priority_queue  

using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
typedef double db;
const int N=5e3,mod=1e9+7;
const db eps=1e-9,pi=acos(-1.0);

mt19937 rnd(time(0));
Il int rint(int l,int r){return rnd()%(r-l+1)+l;}

// bool P1;
Il int qpow(int x,int y){
    int t=1;
    for(;y;y>>=1,x=x*x%mod){
        if(y&1){
            t=t*x%mod;
        }
    }
    return t;
}

int n,a[N+5],jc[N+5],iv[N+5],c[N+5],f[N+5],ans=0;

Il int C(int x,int y){
    return x<0||y<0||x<y?0:jc[x]*iv[y]%mod*iv[x-y]%mod;
}
// bool P2;

signed main(){
    //?????????
    ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    // cout<<abs((&P1)-(&P2))/1024/1024;return 0;
    jc[0]=1;
    for(int i=1;i<=N;i++){
        jc[i]=jc[i-1]*i%mod;
    }
    iv[N]=qpow(jc[N],mod-2);
    for(int i=N-1;~i;i--){
        iv[i]=iv[i+1]*(i+1)%mod;
    }
    cin>>n;
    for(int i=1;i<=n;i++){
        cin>>a[i],c[++a[i]]++;
    }
    f[0]=1;
    for(int i=1;i<=N;i++){
        for(int j=n;j;j--){
            f[j]=(f[j]+f[j-1]*c[i]%mod)%mod;
        }
    }
    for(int i=0;i<=n;i++){
        // cout<<f[i]<<' ';
        if(i&1){
            ans=(ans-f[i]*jc[n-i]%mod+mod)%mod;
        }else{
            ans=(ans+f[i]*jc[n-i]%mod)%mod;
        }
    }
    cout<<ans;
    return 0;
}