#include <cassert>
#include <cmath>
#include <algorithm>
#include <iostream>
#include <iomanip>
#include <limits.h>
#include <map>
#include <queue>
#include <set>
#include <string.h>
#include <vector>

using namespace std;
typedef long long ll;

const ll MOD = 1000000007;

struct Node {
  int id;
  ll val;

  Node(int id = -1, ll val = -1) {
    this->id = id;
    this->val = val;
  }

  bool operator>(const Node &n) const {
    return val > n.val;
  }
};

int main() {
  int N, K;
  cin >> N >> K;

  vector<ll> X;
  ll x;
  for (int i = 0; i < N; ++i) {
    cin >> x;
    X.push_back(x);
  }

  vector<ll> A;
  ll a;
  for (int i = 0; i < N; ++i) {
    cin >> a;
    A.push_back(a);
  }

  priority_queue <Node, vector<Node>, greater<Node>> pque;

  for (int i = 0; i < N; ++i) {
    x = X[i];
    a = A[i];

    pque.push(Node(i, abs(x - X[K - 1])));
  }

  ll l = X[K - 1];
  ll r = X[K - 1];
  int ans = 0;

  while (!pque.empty()) {
    Node node = pque.top();
    pque.pop();
    x = X[node.id];
    a = A[node.id];

    if (l <= x && x <= r) {
      ++ans;
      l = min(l, x - a);
      r = max(r, x + a);
    }
  }

  cout << ans << endl;

  return 0;
}