#include <iostream>
#include <sstream>
#include <cstdlib>
#include <algorithm>
#include <cmath>
#include <iomanip>
#include <numeric>
#include <vector>

using namespace std;
#define ll long long
void sherry()
{
    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
}
int main()
{
    sherry();
    ll n, k, max_num = INT_MIN, sum = 0;
    cin >> n >> k;
    ll arr1[n + 2]{}, arr2[n + 2]{1};
    for (ll i = 0; i < n; i++)
    {
        cin >> arr1[i];
    }
    for (ll i = 0; i < n - k + 1; i++)
    {
        cin >> arr2[i];
    }
    for (ll i = 0; i < n; i++)
    {
        if (arr2[i] == 1)
            sum += arr1[i];
        else
        {
            ll number = 0;
            for (ll j = i; j < i + k && j < n; j++)
            {
                if (arr2[j] == 0)
                    number += arr1[j];
            }
            max_num = max(max_num, number);
        }
    }
    cout << sum + max_num;
    return 0;
}