C11ID.cpp

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

typedef long long ll;

const ll MOD = 1000000007;

int main() {
    cin.tie(0)->sync_with_stdio(0);
    int n; cin >> n;
    vector<ll> a(n);
    for (auto &i : a) {
        cin >> i;
    }
    sort(a.begin(), a.end());
    ll ans = 1;
    for (int i = 0; i < n; i++) {
        (ans *= (a[i] - i)) %= MOD;
    }
    cout << ans << '\n';
}