#include <bits/stdc++.h>
#define F first
#define S second
#define pb push_back
#define ppb pop_back
#define ep insert
#define endl '\n'
#define elif else if
#define pow pwr
#define sqrt sqrtt
#define int long long
#define ll long long
typedef unsigned long long ull;
using namespace std;
const int N=3e5+5;
int n,k,a[N],b[N];
bool ans[N];
int32_t main(){
ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
cin>>n>>k;
for (int i=1;i<=n;i++) cin>>a[i];
for (int i=1;i<=n;i++) cin>>b[i];
int mx=LLONG_MIN;
for (int i=1;i+k-1<=n;i++){
multiset<int> s;
int sum=0;
for (int j=i;j<i+k;j++){
s.ep(b[j]);
sum-=a[j];
sum+=b[j];
}
mx=max(mx,sum);
for (int j=i+k;j<=n;j++){
s.ep(b[j]);
sum-=a[j];
sum+=b[j];
int x=*s.begin();
s.erase(s.begin());
sum-=x;
mx=max(mx,sum);
}
}cout<<mx<<endl;
return 0;
}
