#include <iostream>
#include <algorithm>
#include <iomanip>
#include <vector>
#include <queue>
#include <set>
#include <map>
#define N_MAX 200002

using namespace std;
typedef long long ll;

const ll MOD = 1000000007;

ll inv[N_MAX],fac[N_MAX],finv[N_MAX];

void init(){
    fac[0]=fac[1]=1;
    finv[0]=finv[1]=1;
    inv[1]=1;
    for(int i=2;i<N_MAX;i++){
        inv[i]=MOD-inv[MOD%i]*(MOD/i)%MOD;
        fac[i]=fac[i-1]*(ll) i%MOD;
        finv[i]=finv[i-1]*inv[i]%MOD;
    }
}


int N;
int A[5000];
int cnt[5000];
ll dp[2][5005];

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << setprecision(10) << fixed;
    cin >> N;
    init();
    for(int i = 0; i < N; i++) {
        cin >> A[i];
        cnt[A[i]]++;
    }
    dp[0][0] = 1;
    for(int i = 0; i < N; i++){
        for(int j = 0; j <= i; j++){
            dp[(i+1)%2][j] += dp[i%2][j];
            dp[(i+1)%2][j] %= MOD;
            dp[(i+1)%2][j+1] += dp[i%2][j]*cnt[i];
            dp[(i+1)%2][j+1] %= MOD;
        }
    }
    ll ans = 0;
    for(int i = 0; i <= N; i++){
        ll c = dp[N%2][i];
        ll tmp = (fac[N-i]*c)%MOD;
        if(i%2 == 0) ans += tmp;
        else ans -= tmp;
        ans %= MOD;
    }
    cout << (ans+MOD)%MOD << endl;
}