#include <bits/stdc++.h>
using namespace std;
#define int long long
struct SegTree{
    int size;
    vector<int>arr;
    void init(int n){
        size = 1;
        while(size<n)size*=2;
        arr.assign(2*size,-(int)1e18);
    }
    void set(int i, int v, int x, int lx, int rx){
        if(rx-lx==1){
            arr[x] = v;
            return;
        }
        int m = (lx+rx)/2;
        if(i<m){
            set(i,v,2*x+1,lx,m);
        }
        else{
            set(i,v,2*x+2,m,rx);
        }
        arr[x] = max(arr[2*x+1],arr[2*x+2]);
    }
    void set(int i,int v){
        set(i,v,0,0,size);
    }
    int query(int l,int r, int x, int lx, int rx){
        if(lx>=r||l>=rx)return -(int)1e18;
        if(lx>=l&&rx<=r)return arr[x];
        int m = (lx+rx)/2;
        int s1 = query(l,r,2*x+1,lx,m);
        int s2 = query(l,r,2*x+2,m,rx);
        return max(s1,s2);
    }
    int query(int l, int r){
        return query(l,r,0,0,size);
    }
};
signed main(){
    cin.tie(nullptr)->sync_with_stdio(false);
    int n,k,d;
    cin >> n >> k >> d;
    vector<int>h(n+1);
    for(int i = 1; i<=n; i++){
        cin >> h[i];
    }
    SegTree segtree;
    segtree.init(k+5);
    vector<set<pair<int,int>>>sets(k+5);
    vector<int>add(k);// everything in sets[i] has value v + add[i]
    vector<vector<pair<int,int>>>rem(n+5);
    vector<int>t(n+1);
    for(int i = 1; i<n; i++){
        cin >> t[i];
    }
    for(int i = 1; i<=n; i++){
        int dist = h[i];
        add[i%k]-=d;
        segtree.set(i%k,segtree.query(i%k,i%k+1)-d);
        for(auto [dis,idx]: rem[i]){
            sets[idx%k].erase({dis,idx});
            if(sets[idx%k].size()){
                segtree.set(idx%k,(*--sets[idx%k].end()).first + add[idx%k]);
            }
            else{
                segtree.set(idx%k,-(int)1e18);
            }
        }
        
        
        if(i>1){
            dist += segtree.query(0,k);
        }
        int nd = dist-add[i%k];
        sets[i%k].insert({nd,i});
        segtree.set(i%k,(*--sets[i%k].end()).first + add[i%k]);
        rem[t[i]+1+i].push_back({nd,i});
        if(i==n){
            cout << dist << '\n';
        }
    }
    return 0;
}