#include <bits/stdc++.h>

#define rep(i, n) for (int i = 0; i < (n); i++)
#define repr(i, n) for (int i = (n) - 1; i >= 0; i--)
#define range(a) a.begin(), a.end()

using namespace std;
using ll = long long;

int main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(15);
  int N, K; cin >> N >> K; K--;
  vector<ll> X(N); rep(i, N) cin >> X[i];
  vector<ll> A(N); rep(i, N) cin >> A[i];
  int l = K;
  int r = K;
  ll low = X[K] - A[K];
  ll high = X[K] + A[K];
  for (;;) {
    if (l > 0 && low <= X[l - 1] && X[l - 1] <= high) {
      l--;
      low = min(low, X[l] - A[l]);
      high = max(high, X[l] + A[l]);
    } else if (r + 1 < N && low <= X[r + 1] && X[r + 1] <= high) {
      r++;
      low = min(low, X[r] - A[r]);
      high = max(high, X[r] + A[r]);
    } else break;
  }
  cout << r - l + 1 << endl;
}