各路神犇帮我看看这个贪心哪错了，悬关！

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

typedef long long ll;
const ll N = 1e5 + 10;
ll n, d;
ll dis[N], sum[N], val[N];

int main() {
//    freopen("road.in", "r", stdin);
//    freopen("road.out", "w", stdout);

    cin >> n >> d;
    for (int i = 2; i <= n; i ++) {
        cin >> dis[i];
        sum[i] = sum[i-1] + dis[i];
    }
    for (int i = 1; i <= n; i ++) {
        cin >> val[i];
    }

    ll ans = 0;
    val[0] = 0x3f3f3f3f;
    ll pos = 1, prepos = 0, leftoil = 0;
    for (; pos <= n; pos++) {
        if (val[pos] < val[prepos]) {
            if(prepos!=1)leftoil = (sum[pos] - sum[prepos]) % d;
            ans += max(0ll, (ll(ceil(1.0 * (sum[pos] - sum[prepos] - leftoil) / d)))) * val[prepos];
            prepos = pos;
        }
    }
    cout << ans << endl;
    return 0;
}