#include <bits/stdc++.h>
#define int long long
using namespace std;
const int maxn = 1e6 + 5;

int dp[maxn], a[maxn], t[maxn];
int n,k,d;
priority_queue<pair<int,int>,vector<pair<int,int>>,less<pair<int,int>> > pq[maxn], pq2;
vector <pair<int,int>> lazy[maxn];

signed main()
{
    ios_base::sync_with_stdio(NULL);
    cin.tie(nullptr); cout.tie(nullptr);
    cin >> n >> k >> d;
    for (int i = 1; i <= n; i++) cin >> a[i];
    for (int j = 1; j < n; j++) cin >> t[j];
    fill_n(dp,n+1,-1e18);
    pq2.push({0, 1});
    for (int i = 1; i <= n; i++)
    {
//        cout << i << " :> " << endl;
        while (!pq[i%k].empty() && i > pq[i%k].top().second) pq[i%k].pop();
        if (!pq[i%k].empty()) pq2.push({-(i-1)/k*d + pq[i%k].top().first, i+k-1});
        for (pair<int,int> j:lazy[i]) pq2.push(j);
        while (!pq2.empty() && i > pq2.top().second) pq2.pop();
        dp[i] = max(dp[i], pq2.top().first + a[i]);
        if (i == n) continue;
        int lo = (t[i]) / k * k;
        lazy[max(i + 1, i + lo)].push_back({dp[i] - lo / k * d, i + t[i]});
        if (lo > 0) pq2.push({dp[i], i + k - 1});
        pq[i%k].push({dp[i]+(i-1)/k*d,i+lo-1});
    }
    cout << dp[n] << '\n';

}

/**
15 4 3
-8225 -8961 -5537 -5621 -8143 -5214 -5538 -6912 -6601 -8839 -7872 -7867 -9553 -9793 -7333
4 5 7 4 2 5 1 2 4 5 2 1 2 4
-29940
-29928
**/