A题

思路：

毫无疑问，先把小的数加起来再依次乘最优，证明：

Code:

#include <iostream>
#include <cstdio>
#include <algorithm>
#define ll long long

using namespace std;

const ll mod = 998244353;
const int N = 5e5 + 10;
ll a[N], n;
ll ans;

int main()
{
    scanf("%lld", &n);
    for (int i = 1; i <= n; ++ i)
    {
        scanf("%lld", &a[i]);
    }
    sort(a + 1, a + n + 1);
    for (int i = 1; i <= (n >> 1); ++ i)
    {
        ans += a[i];
    }
    ans %= mod;
    for (int i = (n >> 1) + 1; i <= n; ++ i)
    {
        ans = ans * a[i] % mod;
    }
    cout << ans;
    return 0;
}