哇，这就是 5p 参考代码

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

typedef long long LL;
const int maxn = 100000 + 100;
const int maxm = 1000 + 100;
const LL MOD = 998244853;
int n, m;
LL a[maxn], p[maxn], dp[2][maxm];

int main() {
#ifdef ExRoc
    freopen("test.txt", "r", stdin);
#endif // ExRoc
    ios::sync_with_stdio(false);

    cin >> n >> m;
    for (int i = 1; i <= n; ++i) {
        cin >> a[i];
        a[i] %= m;
    }
    for (int i = 1; i <= n; ++i) {
        cin >> p[i];
        p[i] %= MOD;
    }
    dp[0][0] = 1;
    for (int i = 1; i <= n; ++i) {
        int nowi = i % 2;
        int prei = nowi ^ 1;
        for (int j = 0; j < m; ++j) {
            dp[nowi][j] = (dp[prei][j] * ((((1 - p[i]) % MOD) + MOD) % MOD) % MOD + dp[prei][(j - a[i] + m) % m] * p[i] % MOD) % MOD;
        }
    }
    cout << dp[n & 1][0] << endl;

    return 0;
}