#include<bits/stdc++.h>
using namespace std;
const int N=5050;
const int mod=1e9+7;
int n,m,g[N][N],f[N],b[N],fac[N];
signed main(){
    ios::sync_with_stdio(false);cin.tie(0),cout.tie(0);
    cin>>n;
    for(int i=1;i<=n;++i){
        int x;cin>>x;++x;++b[x];
    }
    g[0][0]=1;
    for(int i=1;i<=n;++i){
        g[i][0]=g[i-1][0];
        for(int j=1;j<=n;++j){
            g[i][j]=(0ll+1ll*g[i-1][j-1]*b[i]%mod+g[i-1][j])%mod;
        }
    }
    fac[0]=1;
    for(int i=1;i<N;++i)fac[i]=1ll*fac[i-1]*i%mod;
    for(int i=0;i<=n;++i)f[i]=1ll*fac[n-i]*g[n][i]%mod;
    int ans=0;
    for(int i=0;i<=n;++i){
        if(i&1)ans=(0ll+ans+mod-f[i])%mod;
        else ans=(0ll+ans+f[i])%mod;
    }
    cout<<ans;
    return 0;
}