import java.io.IOException;
import java.util.Scanner;

class Main{
    public static void main(String args[]) throws IOException{
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt(), k = sc.nextInt()-1;
        long x[] = new long[n];
        long a[] = new long[n];
        for(int i = 0; i < n; i++){
            x[i] = sc.nextLong();
        }
        for(int i = 0; i < n; i++){
            a[i] = sc.nextLong();
        }
        int l = k, r = k;
        long ld = x[k]-a[k], rd = x[k]+a[k];
        boolean update = true;
        while(update){
            update = false;
            while(l-1 >= 0 && ld <= x[l-1]){
                update = true;
                l--;
                ld = Math.min(ld, x[l]-a[l]);
                rd = Math.max(rd, x[l]+a[l]);
            }
            while(r+1 < n && x[r+1] <= rd){
                update = true;
                r++;
                rd = Math.max(rd, x[r]+a[r]);
                ld = Math.min(ld, x[r]-a[r]);
            }
        }
        System.out.println(r-l+1);
    }
}