#include<iostream>
#include<cmath>
#include<iomanip>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<vector>
#include<utility>

#define ll long long
#define sz(x) int(x.size())
#define all(x) x.begin(),x.end()
#define rall(s)  s.rbegin(), s.rend()
#define ceill(n, m) (((n) / (m)) + ((n) % (m) ? 1 : 0))
using namespace std;

void Fast_IO(){
    ios_base::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
    #ifndef ONLINE_JUDGE
        freopen("input.txt", "r", stdin), freopen("output.txt", "w", stdout);
    #endif
}





void solve(){
    ll n,k; cin>>n>>k;
    vector<ll>v(n+1);
    vector<ll>slept(n+1);
    vector<ll>prefix(n+1);
     ll res =0;
    ll maxi = -__LONG_LONG_MAX__;
    for(int i=1; i<=n;i++){
        cin>>v[i];
    }
    for(int i=1; i<=n; i++){
        cin>>slept[i];
        if(slept[i] == 1 ){
            res += v[i];
        }
        if(slept[i]==0){
            prefix[i]=prefix[i-1] + v[i];
        }else prefix[i]=prefix[i-1];
    }

    // for(int i=1; i<=n;i++) cout<<prefix[i]<<' ';
    // cout<<'\n';
    for(int i=1; i<=n-k+1; i++){
            if(prefix[i+k-1]-prefix[i-1]>maxi){
            maxi = prefix[i+k-1]-prefix[i-1];
            }
            // cout<<prefix[i+k-1]-prefix[i-1]<<'\n';
        // cout<<maxi<<'\n';

    }


    cout<<res+maxi;


}

int main(){
    Fast_IO();
int t =1;
//cin>>t;
while(t--){
solve();
}
return 0;
}