奇怪的逆元题目求优化

#include <bits/stdc++.h>
using namespace std;
#define int long long
int fac[5000010];
const int mod = 1e9 + 7;
inline int qmi(int a, int b) {
    int res = 1;
    while (b) {
        if (b & 1) {
            res = res * a % mod;
        }
        a = a * a % mod;
        b >>= 1;
    }
    return res;
}
signed main() {
    ios::sync_with_stdio(false);
    ios_base::sync_with_stdio(false);
    cin.tie(0), cout.tie(0);
    int n, ans = 0, a;
    cin >> n;
    fac[0] = 1;
    for (int i = 1; i <= n; i++) {
        fac[i] = fac[i - 1] * 998244353 % mod;
    }
    for (int i = 1; i <= n; i++) {
        cin >> a;
        ans = (ans + qmi(a, mod - 2) * fac[n - i] % mod);
    }
    cout << ans % mod;
    return 0;
}