#include<iostream>
#include<stdio.h>
#include<vector>
using namespace std;
int main(void)
{
int n,k;
cin>>n>>k;
vector<int> score(n,0);
vector<int> sleep(n,0);
for(int i=0;i<n;i++)
cin>>score[i];
for(int i=0;i<n;i++)
cin>>sleep[i];
int res = 0;
int extra = 0;
int extra_max = 0;
for(int i=0;i<k;i++)
{
if(!sleep[i])
extra+=score[i];
}
if(sleep[0])
res+=score[0];
for(int i=1;i<n;i++)
{
if(sleep[i])
res+=score[i];
if(i+k-1<=n-1)
{
if(!sleep[i-1]) extra-=score[i-1];
if(!sleep[i+k-1]) extra+=score[i+k-1];
}
extra_max = max(extra,extra_max);
}
cout<<extra_max+res<<endl;
return 0;
}