#pragma GCC optimize("O3")
#pragma GCC optimize ("unroll-loops")
#pragma GCC target("avx,avx2,fma")

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

#define ll long long
#define ld long double


const int N = 1e5 + 5, lg = 17, mod = 1e9 + 7;

ll n, k, d, h[N], t[N];
ll dp[N], delta[N];
vector<pair<int, ll>> del[N];
multiset<ll> ans[N];
multiset<ll> st;
ll seg[N << 2];
void update(int node, int s, int e, int i, ll val) {
    if(s == e) {
        seg[node] = val;
        return;
    }
    int mid = s + e >> 1;
    if(i <= mid)
        update(node << 1, s, mid, i, val);
    else
        update(node << 1 | 1, mid + 1, e, i, val);
    seg[node] = max(seg[node << 1], seg[node << 1 | 1]);
}
int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    cin >> n >> k >> d;
    for(int i = 1;i <= n;i++)
        cin >> h[i];
    for(int i = 1;i < n;i++)
        cin >> t[i];
    fill(seg, seg + (N * 4), -1e16);
    dp[1] = h[1];
    ans[1 % k].insert(dp[1]);
    update(1, 0, k - 1, 1 % k, dp[1]);
    del[t[1] + 2].push_back({1 % k, dp[1]});
    for(int i = 2;i <= n;i++) {
        for(auto j : del[i]) {
            int idx = j.first;
            ll val = j.second;
            ans[idx].erase(ans[idx].find(val));
            if(ans[idx].empty())
                update(1, 0, k - 1, idx, -1e16);
            else
                update(1, 0, k - 1, idx, *ans[idx].rbegin() + delta[idx]);
        }
        int cur = i % k;
        delta[cur] -= d;
        if(!ans[cur].empty())
            update(1, 0, k - 1, cur, *ans[cur].rbegin() + delta[cur]);
        dp[i] = seg[1] + h[i];

        ans[cur].insert(dp[i] - delta[cur]);

        if(ans[cur].empty())
            update(1, 0, k - 1, cur, -1e16);
        else
            update(1, 0, k - 1, cur, *ans[cur].rbegin() + delta[cur]);
        del[i + t[i] + 1].push_back({cur, dp[i] - delta[cur]});
    }
    cout << dp[n];
    return 0;
}