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;
    }
    // ==================================================================
    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());
		}
    	int l = K, r = K;
    	long lval = X[K] - A[K];
    	long rval = X[K] + A[K];
    	boolean flag = true;
    	while(flag) {
    		flag = false;
    		while(l > 0 && X[l-1] >= lval) {
    			flag = true;
    			l--;
    			lval = Math.min(lval, X[l] - A[l]);
    			rval = Math.max(rval, X[l] + A[l]);
    		}
    		while(r < N - 1 && X[r+1] <= rval) {
    			flag = true;
    			r++;
    			lval = Math.min(lval, X[r] - A[r]);
    			rval = Math.max(rval, X[r] + A[r]);
    		}
    	}
    	out.println(r - l + 1);
    }
}