#include <bits/stdc++.h>
using namespace std;
using lint = long long int;
struct fast_ios { fast_ios(){ cin.tie(0); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_;
#define FOR(i, begin, end) for(int i=(begin);i<(end);i++)
#define IFOR(i, begin, end) for(int i=(end)-1;i>=(begin);i--)
#define REP(i, n) FOR(i,0,n)
#define IREP(i, n) IFOR(i,0,n)

int N;
constexpr int Nmax = 5000;
map<int, int> A;
constexpr lint MOD = 1000000007;

vector<lint> fac, facInv, inv;
void facInit(int nmax)
{
    fac = facInv = inv = vector<lint>(nmax + 1, 1);
    for (int i = 2; i <= nmax; i++)
    {
        fac[i] = fac[i-1] * i % MOD;
        inv[i] = MOD - inv[MOD%i] * (MOD/i) % MOD;
        facInv[i] = facInv[i-1] * inv[i] % MOD;
    }
}
lint nCr(int n, int r)
{
    if (n<r || r<0) return 0;
    return (fac[n] * facInv[r] % MOD) * facInv[n-r] % MOD;
}

signed main()
{
    cin >> N;
    REP(i, N) {
        int tmp;
        cin >> tmp;
        if (tmp < N) A[tmp]++;
    }

    lint dp[Nmax + 1];
    memset(dp, 0, sizeof(dp));

    dp[0] = 1;
    for (auto v : A)
    {
        lint n = v.second;
        IREP(i, Nmax) if (dp[i]) (dp[i + 1] += n * dp[i]) %= MOD;
    }

    lint ans = 0;
    facInit(Nmax);
    REP(i, N + 1) // i人が悪い番号になる
    {
        lint tmp = dp[i] * fac[N - i] % MOD;
        if (i & 1) (ans += (MOD - tmp)) %= MOD;
        else (ans += tmp) %= MOD;
    }
    cout << ans << endl;
}