//#pragma GCC optimize("Ofast")

#ifdef LOCAL
#include "debug.h"
#else
#include <bits/stdc++.h>
#define debug(x...)
#endif

//#define int ll

using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair <int, int> pii;
#define sz(x) int((x).size())

#ifdef ONLINE_JUDGE
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
#else
mt19937 rng(1000 - 7);
#endif

const int N = 3e3 + 10;
const int M = 5e2 + 10;
//const int MOD2 = 998244353;
const int MOD = 1e9 + 7;
const ld eps = 1e-6;
const pii dir[] = { { 0, 1 }, { 0, -1 }, { 1, 0 }, { -1, 0 } };

int n, a[N];
ll dp[N][N], fact[N], C[N][N];

signed main() {
#ifdef LOCAL
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif
    cout << fixed << setprecision(9);
    ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);

    fact[0] = 1;
    for (int i = 1; i < N; i++) {
        fact[i] = (fact[i - 1] * i) % MOD;
    }

    for (int i = 0; i < N; i++) {
        C[i][0] = C[i][i] = 1;
    }

    for (int i = 1; i < N; i++) {
        for (int j = 1; j < i; j++) {
            C[i][j] = (C[i - 1][j] + C[i - 1][j - 1]) % MOD;
        }
    }
    
    cin >> n;
    for (int i = 0, x; i < n; i++) {
        cin >> x;
        a[x]++;
    }

    auto sqr = [=] (ll x) {
        return (x * x) % MOD;
    };

    dp[0][0] = 1;
    for (int i = 1; i <= n; i++) {
        for (int j = 0; j <= n; j++) {
            for (int k = 0; k <= min(a[i], j); k++) {
                dp[i][j] = (dp[i][j] + 
                            (dp[i - 1][j - k] * sqr(C[a[i]][k])) % MOD * fact[k]) % MOD;
            }
        }
    }

    ll ans = (dp[n][0] * fact[n]) % MOD;
    for (int i = 1; i <= n; i++) {
        if (i % 2) {
            ans = (ans - (dp[n][i] * fact[n - i]) % MOD + MOD) % MOD;
        }
        else {
            ans = (ans + (dp[n][i] * fact[n - i]) % MOD) % MOD;
        }
    }

    cout << ans << endl;

    return 0;
}