source_code: import java.io.*;
  import java.util.*;
  
  public class LectureSleep {
  
      static class InputReader {
          BufferedReader reader;
          StringTokenizer tokenizer;
  
          public InputReader(InputStream stream) {
              reader = new BufferedReader(new InputStreamReader(stream), 32768);
              tokenizer = null;
          }
  
          String next() {
              while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                  try {
                      tokenizer = new StringTokenizer(reader.readLine());
                  } catch (IOException e) {
                      throw new RuntimeException(e);
                  }
              }
              return tokenizer.nextToken();
          }
  
          public int nextInt() {
              return Integer.parseInt(next());
          }
  
          public long nextLong() {
              return Long.parseLong(next());
          }
  
          public double nextDouble() {
              return Double.parseDouble(next());
          }
  
          public float nextFloat() {
              return Float.parseFloat(next());
          }
  
      }
  
      static InputReader r = new InputReader(System.in);
      static PrintWriter pw = new PrintWriter(System.out);
  
  
      public static void main(String[] args) {
          int n = r.nextInt(); // duration of lecture
          int k = r.nextInt(); // number of minutes keep mishka awake
          int[] theorems = new int[n+1];
          for(int i = 1; i <= n; i++){
              theorems[i] = r.nextInt();
          }
          int[] mishka = new int[n+1];
          for(int i = 1; i <= n; i++){
              mishka[i] = r.nextInt();
          }
          int[] sums = new int[n+1];
          for(int i = 1; i <= n; i++){
              if(mishka[i] == 0){
                  sums[i] = sums[i-1] + theorems[i];
              } else{
                  sums[i] = sums[i-1];
              }
          }
          int max = 0;
          for(int i = 1; i <= n-k+1; i++){
              int sum = sums[i+k-1] - sums[i-1];
              max = Math.max(max, sum);
          }
          int totalSum = 0;
          for(int i = 1; i <= n; i++){
              if(mishka[i] == 1){
                  totalSum += theorems[i];
              }
          }
  
          pw.println(totalSum + max);
  
          pw.close();
      }
  }