#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;
  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];
  }

  vector<pair<long long , long long> > p(n);

  for (int i = 0; i < n; i++) {
    p[i]= make_pair(x[i] - a[i] , x[i] + a[i]);
  }

  k--;

  /*
  if (a[k] == 0) {
    cout << 1 << endl;
    return 0;
  }
  */

  long long mn = p[k].first;
  for (int i = k; i < n - 1; i++) {
    if (x[i + 1] <= p[i].second && mn >= p[i + 1].first) {
      mn = p[i].first;
    } else {
      break;
    }
  }

  long long mx = p[k].second;
  for (int i = k; i >= 1; i--) {
    if (x[i - 1] >= p[i].first && mx <= p[i - 1].second) {
      mx = p[i - 1].second;
    } else {
      break;
    }
  }

  vector<int> cnt(n , 0);
  cnt[k] = 1;

  for (int i = k; i < n; i++) {
    if (x[i] <= mx) {
      cnt[i] = cnt[k];
      if (p[i].second >= mx) {
        mx = p[i].second;
      }
    }
  }

  for (int i = k; i >= 0; i--) {
    if (x[i] >= mn) {
      cnt[i] = cnt[k];
      if (p[i].first <= mn) {
        mn = p[i].first;
      }
    }
  }
  
  int ans = 0;
  for (int i = 0; i < n; i++) {
    ans += cnt[i] > 0;
  }
  cout << ans << endl;
  return 0;
}