#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
//#include<cctype>
#include<climits>
#include<iostream>
#include<string>
#include<vector>
#include<map>
//#include<list>
#include<queue>
#include<deque>
#include<algorithm>
//#include<numeric>
#include<utility>
#include<complex>
//#include<memory>
#include<functional>
#include<cassert>
#include<set>

const int dx[] = {1, 0, -1, 0};
const int dy[] = {0, 1, 0, -1};
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef pair<int, int> pii;
typedef complex<double> C;

const int MAXN = 5005;
const ll MOD = 1e9+7;
int N;
int cnt[MAXN];

ll dp[2][MAXN];
ll fact[MAXN];

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    fact[0] = 1;
    for (int i = 1; i < MAXN; i++) {
        fact[i] = (fact[i-1] * i) % MOD;
    }
    cin >> N;
    for (int i = 0; i < N; i++) {
        int a;
        cin >> a;
        cnt[a]++;
    }
    dp[0][0] = 1;
    for (int i = 0; i < N; i++) {
        int cur = i%2;
        int tar = (1^cur);
        memset(dp[tar], 0, sizeof(dp[tar]));
        for (int j = 0; j <= i; j++) {
            (dp[tar][j] += dp[cur][j]) %= MOD;
            (dp[tar][j+1] += dp[cur][j] * cnt[i]) %= MOD;
        }
    }
    ll ans = 0;
    for (int i = 0; i <= N; i++) {
        ll plus = (dp[N%2][i]*fact[N-i]) % MOD;
        if (i%2) plus *= -1;
        (ans += plus) %= MOD;
    }
    if (ans < 0) ans += MOD;
    cout << ans << endl;
    return 0;
}