#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
signed main() {
  ios::sync_with_stdio(false); cin.tie(0);
  int n, k;
  cin >> n >> k;
  vector<long long> x(n);
  for (int i = 0; i < n; i++) {
    cin >> x[i];
  }
  vector<long long> a(n);
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  k--;
  long long cur = x[k] - a[k];
  int ans = 1;
  for (int i = k - 1; i >= 0; i--) {
    if (x[i] >= cur) ans++, cur = x[i] - a[i];
    else break;
  }
  cur = x[k] + a[k];
  for (int i = k + 1; i < n; i++) {
    if (x[i] <= cur) ans++, cur = x[i] + a[i];
    else break;
  }
  cout << ans << endl;
  return 0;
}