#include <bits/stdc++.h>

using namespace std;

using int64 = long long;
const int mod = 1e9 + 7;

const int64 infll = (1LL << 62) - 1;
const int inf = (1 << 30) - 1;

struct IoSetup {
  IoSetup() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
    cerr << fixed << setprecision(10);
  }
} iosetup;


template< typename T1, typename T2 >
ostream &operator<<(ostream &os, const pair< T1, T2 > &p) {
  os << p.first << " " << p.second;
  return os;
}

template< typename T1, typename T2 >
istream &operator>>(istream &is, pair< T1, T2 > &p) {
  is >> p.first >> p.second;
  return is;
}

template< typename T >
ostream &operator<<(ostream &os, const vector< T > &v) {
  for(int i = 0; i < (int) v.size(); i++) {
    os << v[i] << (i + 1 != v.size() ? " " : "");
  }
  return os;
}

template< typename T >
istream &operator>>(istream &is, vector< T > &v) {
  for(T &in : v) is >> in;
  return is;
}

template< typename T1, typename T2 >
inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }

template< typename T1, typename T2 >
inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); }

template< typename T = int64 >
vector< T > make_v(size_t a) {
  return vector< T >(a);
}

template< typename T, typename... Ts >
auto make_v(size_t a, Ts... ts) {
  return vector< decltype(make_v< T >(ts...)) >(a, make_v< T >(ts...));
}

template< typename T, typename V >
typename enable_if< is_class< T >::value == 0 >::type fill_v(T &t, const V &v) {
  t = v;
}

template< typename T, typename V >
typename enable_if< is_class< T >::value != 0 >::type fill_v(T &t, const V &v) {
  for(auto &e : t) fill_v(e, v);
}

template< typename F >
struct FixPoint : F {
  explicit FixPoint(F &&f) : F(forward< F >(f)) {}

  template< typename... Args >
  decltype(auto) operator()(Args &&... args) const {
    return F::operator()(*this, forward< Args >(args)...);
  }
};

template< typename F >
inline decltype(auto) MFP(F &&f) {
  return FixPoint< F >{forward< F >(f)};
}

int main() {
  int N, K;
  cin >> N >> K;
  --K;
  vector< int64 > X(N), A(N);
  cin >> X >> A;

  int ret = 0;

  int p = K + 1, q = K - 1;

  int64 uku = -infll;
  int64 uke = infll;

  bool update = true;
  while(update) {
    update = false;
    while(p < N) {
      int64 r = X[p - 1] + A[p - 1];
      chmax(uku, r);
      chmin(uke, X[p - 1] - A[p - 1]);
      if(uku >= X[p]) {
        ++ret;
        chmax(uku, X[p] + A[p]);
        chmin(uke, X[p] - A[p]);
        ++p;
        update = true;
      } else {
        break;
      }
    }


    while(q >= 0) {
      int64 r = X[q + 1] - A[q + 1];
      chmin(uke, r);
      chmax(uku, X[q + 1] + A[q + 1]);
      if(uke <= X[q]) {
        ++ret;
        chmax(uku, X[q] + A[q]);
        chmin(uke, X[q] - A[q]);
        --q;
        update = true;
      } else {
        break;
      }
    }
  }

  cout << ret + 1 << endl;

}