#include <bits/stdc++.h>
using namespace std;

#include <atcoder/all>
using namespace atcoder;
using mint = modint1000000007;

#define all(x) (x).begin(),(x).end()
#define rep(i, n) for (int i = 0; i < (n); i++)
#define endl "\n"

#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

template <typename T> ostream &operator<<(ostream &os, const vector<T> &vec) {os << "["; for (const auto &v : vec) {os << v << ","; } os << "]"; return os;}
template <typename T, typename U> ostream &operator<<(ostream &os, const pair<T, U> &p) {os << "(" << p.first << ", " << p.second << ")"; return os;}
ll mod_pow(ll a, ll n, ll mod) { ll ret = 1; ll p = a % mod; while (n) { if (n & 1) ret = ret * p % mod; p = p * p % mod; n >>= 1; } return ret; }

const int mod = 1e9 + 7;

void solve() {
    int N; cin >> N; 
    vector<int> cnt(N + 1);
    for (int i = 0; i < N; i++) {
        int x; cin >> x; cnt[x + 1]++;
    }

    vector<mint> fact(100000);
    fact[0] = 1;
    for (int i = 1; i < 100000; i++) {
        fact[i] = fact[i - 1] * i;
    }

    vector<vector<mint>> dp(N + 1, vector<mint>(N + 1));
    dp[0][0] = 1;

    for (int i = 0; i < N; i++) {
        for (int j = 0; j <= N; j++) {
            if (j + 1 <= N) dp[i + 1][j + 1] += dp[i][j] * cnt[i + 1];
            dp[i + 1][j] += dp[i][j];
        }
    }

    mint ans = fact[N];
    for (int i = 1; i <= N; i++) {
        ans += (i % 2 == 1 ? -1 : 1) * dp[N][i] * fact[N - i];
    }
    cout << ans.val() << endl;
}

int main() {
    #ifdef LOCAL_ENV
    cin.exceptions(ios::failbit);
    #endif
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout.setf(ios::fixed);
    cout.precision(16);
    
    solve();
}