import java.util.Arrays;
import java.util.Scanner;

public class KeShui {
	
	public static int max = 0;
	//網易瞌睡
	public static void maxivalue(int [] arr, int k,int [] ks){
		int length = arr.length;
		int tmp = k;
		int sum = 0;
		for (int i = 0; i < length; i++) {
			if(ks[i] == 1){
				sum += arr[i]; 
			}

		}
		for (int i = 0; i < length;i++){ //滑動視窗
			if(ks[i] == 0){
				sum += arr[i];
			}
			if(i >= k - 1){
				max = Math.max(max, sum);
				if(ks[i - (k - 1)] == 0)
					sum -= arr[i - (k - 1)];
			}
		}
	}
	//求一個數組中  三個相連的數的最大值
	public static int get(int [] arr,int k){//最多有三個數之和的最大值  相當於一個滑動視窗
		int max = Integer.MIN_VALUE;
		int sum = 0;
		for (int i = 0; i < arr.length; i++) {// 1 2 3 4 3   k-1=2
			sum += arr[i];
			max = Math.max(max, sum);
			if(i >= k - 1)
				sum -= arr[i - (k - 1)];
		}
		return max;
	}
	
	//除了他清醒外 最多清醒一次 並獲取最大收益
	public static void main(String[] args) {
		  Scanner sc = new Scanner(System.in);
	      String [] str = sc.nextLine().trim().split(" ");
	      int [] arr = new int[str.length];
	      for (int i = 0; i < arr.length; i++) {  // 6 3
		 	 arr[i] = Integer.parseInt(str[i]);
	 	 }
	      String [] cstr = sc.nextLine().trim().split(" ");
	      int [] carr = new int[cstr.length];
	      for (int i = 0; i < carr.length; i++) {  //數值1 3 5 2 5 4
	    	  carr[i] = Integer.parseInt(cstr[i]);
	      }
	      String [] ccstr = sc.nextLine().trim().split(" ");
	      int [] ccarr = new int[ccstr.length];
	      for (int i = 0; i < ccarr.length; i++) {  //數值 1 1 0 1 0 0
	    	  ccarr[i] = Integer.parseInt(ccstr[i]);
	      }
	      
	      maxivalue(carr,arr[1],ccarr);
	      System.out.println(max);
	}
//	public static void main(String[] args) {
//		int arr[] = {1,2,3,4,3,1,1,1,2,2,2,33,3,3,55};
//		System.out.println(get(arr, 3));
//	}
}