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

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n, v, s = 0;
    cin >> n;
    vector<int> cnt(5000);
    vector<mint> fact(n + 1), dp(n + 1);
    fact[0] = dp[0] = 1;
    for(int i = 1; i <= n; i++){
        cin >> v, cnt[v]++;
        fact[i] = fact[i - 1] * i;
    }
    for(int i = 0; i < n; i++){
        if(!cnt[i])continue;
        for(int j = s; j >= 0; j--) dp[j + 1] += dp[j] * cnt[i];
        s++;
    }
    mint ans;
    for(int i = 0; i <= s; i++){
        ans += (i & 1 ? -dp[i] : dp[i]) * fact[n - i]; 
    }
    cout << ans.val() << '\n';
}