#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+k);
    vector<ll>slept(n+k);
    vector<ll>prefix(n+k);
    int start,end;
    ll maxi = -__LONG_LONG_MAX__;
    for(int i=1; i<=n;i++){
        cin>>v[i];
        prefix[i]=prefix[i-1]+v[i];
    }
    for(int i=1; i<=n; i++) cin>>slept[i];
    for(int i=1; i<=n; i++){
            if(prefix[i+k-1]-prefix[i-1]>maxi){
            maxi = prefix[i+k-1]-prefix[i-1];
            start = i,end=i+k-1;
            }


    }
    ll res =0;
    for(int i=1; i<=n; i++){
        if(slept[i] == 1 && (i<start || i>end)){
            res += v[i];
        }
    }
    cout<<res+maxi;


}

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