// includes {{{
#include<iostream>
#include<iomanip>
#include<algorithm>
#include<vector>
#include<stack>
#include<queue>
#include<map>
#include<set>
#include<tuple>
#include<cmath>
#include<random>
#include<cassert>
#include<bitset>
#include<cstdlib>
// #include<deque>
// #include<multiset>
// #include<cstring>
// #include<bits/stdc++.h>
// }}}
using namespace std;
using ll = long long;

constexpr int N = 1e5;
ll a[N], x[N];

int main() {
  std::ios::sync_with_stdio(false), std::cin.tie(0);
  int n, k;
  cin >> n >> k;
  k--;
  using P = pair<ll, ll>;
  set<pair<ll, ll>> v;
  for(int i = 0; i < n; i++) cin >> x[i];
  for(int i = 0; i < n; i++) cin >> a[i], v.emplace(x[i], a[i]);
  ll l = x[k], r = l;
  int ans = 0;
  while(1) {
    auto ite = v.lower_bound(P(l, 0));
    if(ite != v.end() and ite->first <= r) {
      auto p = *ite;
      v.erase(ite);
      l = min(l, p.first - p.second);
      r = max(r, p.first + p.second);
      ans++;
    } else break;
  }
  cout << ans << endl;
  return 0;
}