#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<ll, ll>;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
ll MOD = 1e9+7;
void add(ll &a, ll b)
{
    a = (a+b) % MOD;
}
int main()
{
    int n;
    cin >> n;
    vector<int> cnt(5000, 0);
    rep(i, n)
    {
        int a;
        cin >> a;
        cnt[a]++;
    }
    vector<ll> dp(n+1, 0);
    dp[0] = 1;
    rep(i, n)
    {
        for(int j = i; j >= 0; j--)
        {
            add(dp[j+1], dp[j] * cnt[i] % MOD);
        }
    }
    vector<ll> p(n+1, 0);
    p[0] = 1;
    for(int i = 1; i <= n; i++) p[i] = p[i-1] * i % MOD;
    ll ans = 0;
    rep(i, n+1)
    {
        if(i % 2) add(ans, -dp[i] * p[n-i] % MOD);
        else add(ans, dp[i] * p[n-i] % MOD);
    }
    add(ans, MOD);
    cout << ans << endl;
}