#include <iostream>
#include <vector>
#include <algorithm>
#include <functional>
#include <queue>
#include <map>
#include <cmath>
#include <iomanip>
#include <set>

using namespace std;

int main() {
  int n , k;
  cin >> n >> k;
  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];
  }

  int i = k , j = k;
  int ans = 0;
  long long mx = -1e18;
  long long mn = 1e18;
  int t = 2 * n;
  while (t--) {
    mx = max(mx , x[i] + a[i]);
    if (i < n - 1 && x[i + 1] <= mx) {
      i++;
      mn = min(mn , x[i] - a[i]);
    }
    mn = min(mn , x[j] - a[j]);
    if (j >= 1 && x[j - 1] >= mn) {
      j--;
      mx = max(mx , x[j] + a[j]);
    }
  }
  cout << i - j + 1 << endl;
  return 0;
}