import java.io.InputStream;
import java.io.PrintWriter;
import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.PriorityQueue;
import java.util.Scanner;
import java.util.Set;
import java.util.Stack;
import java.util.TreeMap;
import java.util.TreeSet;

import static java.util.Comparator.*;

public class Main {
    public static void main(String[] args) {
        PrintWriter out = new PrintWriter(System.out);
        Solver solver = new Solver(System.in, out);
        solver.solve();
        out.close();
    }
}
class Solver {
	Scanner sc;
	PrintWriter out;
    public Solver(InputStream in, PrintWriter out) {
    	sc = new Scanner(in);
    	this.out = out;
    }
    // ==================================================================
    TreeMap<Long, Long> map = new TreeMap<>();
    public void solve() {
    	int N = Integer.parseInt(sc.next());
    	int K = Integer.parseInt(sc.next()) - 1;
    	long[] X = new long[N];
    	long[] A = new long[N];
    	for (int i = 0; i < N; i++) {
			X[i] = Long.parseLong(sc.next());
		}
    	for (int i = 0; i < N; i++) {
			A[i] = Long.parseLong(sc.next());
		}
    	for (int i = 0; i < N; i++) {
    		map.put(X[i], A[i]);
    	}
    	long min = X[K], svMin = min;
    	long max = X[K], svMax = max;
    	long lkey = X[K] - A[K] - 1;
    	long rkey = X[K] + A[K] + 1;
    	Entry<Long, Long> low;
    	Entry<Long, Long> high;
    	while(true) {
//    		out.println("min = " + min + "  lkey = " + lkey + "  max = " + max + "  rkey = " + rkey);
    		low = map.higherEntry(lkey);
    		high = map.lowerEntry(rkey);
    		if(low != null) {
//        		out.println(" low : X = " + low.getKey() + "  A = " + low.getValue());
        		min = Math.min(min, low.getKey());
        		lkey = Math.min(lkey, low.getKey() - low.getValue() - 1);
        		max = Math.max(max, low.getKey());
        		rkey = Math.max(rkey, low.getKey() + low.getValue() + 1);
    		}
    		if(high != null) {
//        		out.println(" high : X = " + high.getKey() + "  A = " + high.getValue());
        		min = Math.min(min, high.getKey());
        		lkey = Math.min(lkey, high.getKey() - high.getValue() - 1);
        		max = Math.max(max, high.getKey());
        		rkey = Math.max(rkey, high.getKey() + high.getValue() + 1);
    		}
    		if(min == svMin && max == svMax)	break;
    		svMin = min;	svMax = max;
    	}
    	int ans = 0;
    	for (int i = 0; i < N; i++) {
			if(X[i] >= min && X[i] <= max)	ans++;
		}
    	out.println(ans);
    }
    
    class PP{
    	public int key, val;
    	public PP(int key, int val) {
    		this.key = key;
    		this.val = val;
    	}
		public int getKey() {
			return key;
		}
		public void setKey(int key) {
			this.key = key;
		}
		public int getVal() {
			return val;
		}
		public void setVal(int val) {
			this.val = val;
		}
    }
}