use std::vec::Vec;
use std::cmp::min;
use std::cmp::max;


fn read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}

fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    read::<String>().split_whitespace().map(|e| e.parse().ok().unwrap()).collect()
}

fn main() {
  let (n, k) = {
    let v: Vec<usize> = read_vec();
    (v[0], v[1] - 1)
  };
  let x: Vec<i64> = read_vec();
  let a: Vec<i64> = read_vec();

  let mut wave_range_right = x[k] + a[k];
  let mut wave_range_left = x[k] - a[k];
  // 右側のカエル
  for i in k+1..n {
    if wave_range_right >= x[i] {
      wave_range_right = max(wave_range_right, x[i] + a[i]);
      wave_range_left = min(wave_range_left, x[i] - a[i]);
    }
  }

  // 左側のカエル
  for i in (0..k).rev() {
    if wave_range_left <= x[i] {
      wave_range_right = max(wave_range_right, x[i] + a[i]);
      wave_range_left = min(wave_range_left, x[i] - a[i]);
    }
  }
  let mut ans = 0;
  for i in 0..n {
    if wave_range_left <= x[i] && x[i] <= wave_range_right {
      ans += 1;
    }
  }
  println!("{}", ans);
  //println!("{}", wave_range_left);
  //println!("{}", wave_range_right);
}