#include <bits/stdc++.h>
 
using namespace std;
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
 
mt19937 rng((int) chrono::steady_clock::now().time_since_epoch().count());
    
const int MOD = 1e9 + 7;
const int MAXN = 1e5 + 5;
const ll INF = 2e18;

ll a[4*MAXN], lz1[4*MAXN], lz2[4*MAXN], a1[4*MAXN], a2[4*MAXN];
 
void build(int node, int i, int j) {
	if (i == j) a[node] = -INF;
	else {
		int m = (i+j)/2;
		build(2*node, i, m), build(2*node+1, m+1, j);
		a[node] = max(a[2*node], a[2*node+1]);
	}
}
 
void push(int node, int i, int j) {
	if (a1[node]) {
		a[node] = lz1[node];
		if (i != j) {
			lz1[2*node] = lz1[2*node+1] = lz1[node];
			a1[2*node] = a1[2*node+1] = 1;
			lz2[2*node] = lz2[2*node+1] = a2[2*node] = a2[2*node+1] = 0;
		}
		lz2[node] = lz1[node] = a2[node] = a1[node] = 0;
	}
	if (a2[node]) {
		a[node] += lz2[node];
		if (i != j) {
			if (a1[2*node]) {
				lz1[2*node] += lz2[node];
				lz2[2*node] = 0;
				a2[2*node] = 0;
			}
			else {
				lz2[2*node] += lz2[node];
				a2[2*node] = 1;
			}
			if (a1[2*node+1]) {
				lz1[2*node+1] += lz2[node];
				lz2[2*node+1] = 0;
				a2[2*node+1] = 0;
			}
			else {
				lz2[2*node+1] += lz2[node];
				a2[2*node+1] = 1;
			}
		}
		lz2[node] = 0;
		a2[node] = 0;
	}
}

ll query(int node, int i, int j, int ini, int fim) {
	push(node, i, j);
	if (j < ini || i > fim) return -INF;
	if (ini <= i && j <= fim) return a[node];
	else {
		int m = (i+j)/2;
		return max(query(2*node, i, m, ini, fim), query(2*node+1, m+1, j, ini, fim));
	}
}

void update(int node, int i, int j, int ini, int fim, ll val, bool set) {
    push(node, i, j);
	if (j < ini || i > fim) return;
	if (ini <= i && j <= fim) {
		if (set) {
			lz1[node] = val;
			a1[node] = true;
		}
		else {
			if (a1[node]) lz1[node] += val;
			else {
				lz2[node] += val;
				a2[node] = true;
			}
		}
		push(node, i, j);
	}
	else {
		int m = (i+j)/2;
		update(2*node, i, m, ini, fim, val ,set);
		update(2*node+1, m+1, j, ini, fim, val, set);
		a[node] = max(a[2*node], a[2*node+1]);
	}
}

ll n, k, d, h[MAXN], t[MAXN], id[MAXN], dp[MAXN];
vector<int> del[MAXN];

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin >> n >> k >> d;
    for (int i = 0; i < n; i++) {
        cin >> h[i];
    }
    for (int i = 0; i < n - 1; i++) {
        cin >> t[i];
    }
    build(1, 0, n - 1);
    int at = 0;
    for (int i = 0; i < k; i++) {
        int x = i;
        while (x < n) {
            id[x] = at++;
            x += k;
        }
    }
    dp[0] = h[0];
    update(1, 0, n - 1, id[0], id[0], dp[0], true);
    del[0 + t[0]].push_back(0);
    for (int i = 1; i < n; i++) {
        // update the dudes
        if (i >= k)
            update(1, 0, n - 1, id[i % k], id[i] - 1, -d, false);

        // calc dp[i]
        dp[i] = h[i] + query(1, 0, n - 1, 0, n - 1);

        // update seg
        update(1, 0, n - 1, id[i], id[i], dp[i], true);

        // delete elements
        for (int x : del[i]) {
            update(1, 0, n - 1, id[x], id[x], -INF, true);
        }
    }
    cout << dp[n - 1] << '\n';
    return 0;
}