#include <algorithm>
#include <bitset>
#include <cassert>
#include <cctype>
#include <chrono>
#define _USE_MATH_DEFINES
#include <cmath>
#include <cstdio>
#include <cstring>
#include <ctime>
#include <deque>
#include <functional>
#include <iostream>
#include <iterator>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <string>
#include <tuple>
#include <utility>
#include <vector>
using namespace std;

#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()

const int INF = 0x3f3f3f3f;
const long long LINF = 0x3f3f3f3f3f3f3f3fLL;
const double EPS = 1e-8;
const int MOD = 1000000007; // 998244353;
const int dy[] = {1, 0, -1, 0}, dx[] = {0, -1, 0, 1};
/*-------------------------------------------------*/
int main() {
  cin.tie(0); ios::sync_with_stdio(false);
  // freopen("input.txt", "r", stdin);

  int n, k; cin >> n >> k; --k;
  vector<long long> x(n), a(n), comp;
  REP(i, n) cin >> x[i];
  REP(i, n) cin >> a[i];
  REP(i, n) {
    comp.emplace_back(x[i] - a[i]);
    comp.emplace_back(x[i]);
    comp.emplace_back(x[i] + a[i]);
  }
  sort(ALL(comp));
  comp.erase(unique(ALL(comp)), comp.end());
  int sz = comp.size();
  vector<int> l(n), r(n);
  vector<vector<int> > pos(sz);
  REP(i, n) {
    l[i] = lower_bound(ALL(comp), x[i] - a[i]) - comp.begin();
    r[i] = lower_bound(ALL(comp), x[i] + a[i]) - comp.begin();
    x[i] = lower_bound(ALL(comp), x[i]) - comp.begin();
    pos[x[i]].emplace_back(i);
  }
  int left = l[k], old_l = l[k], right = r[k], old_r = r[k];
  FOR(i, old_l, old_r + 1) {
    for (int e : pos[i]) {
      left = min(left, l[e]);
      right = max(right, r[e]);
    }
  }
  bool update = true;
  while (update) {
    update = false;
    int tmp_l = left, tmp_r = right;
    FOR(i, tmp_l, old_l) if (!pos[i].empty()) {
      for (int e : pos[i]) {
        if (l[e] < left) {
          left = l[e];
          update = true;
        }
        if (right < r[e]) {
          right = r[e];
          update = true;
        }
      }
    }
    FOR(i, old_r + 1, tmp_r + 1) if (!pos[i].empty()) {
      for (int e : pos[i]) {
        if (l[e] < left) {
          left = l[e];
          update = true;
        }
        if (right < r[e]) {
          right = r[e];
          update = true;
        }
      }
    }
    old_l = tmp_l;
    old_r = tmp_r;
  }
  // cout << left << ' ' << right << '\n';
  int ans = 0;
  REP(i, n) {
    if (left <= x[i] && x[i] <= right) ++ans;
  }
  cout << ans << '\n';
  return 0;
}