/**
  @file 871.cpp
  @title  No.871 かえるのうた - yukicoder
  @url https://yukicoder.me/problems/no/871
**/

#include <bits/stdc++.h>
using namespace std;

typedef long long LL;
#define ALL(obj) (obj).begin(), (obj).end()
#define RALL(x) (x).rbegin(), (x).rend()
#define SZ(x) ((int)(x).size())

#define REPI(i, a, b) for (LL i = LL(a); i < LL(b); ++i)
#define REP(i, N) for (LL i = LL(0); i < LL(N); ++i)
#define REPS(i, N) for (int i = 1; i <= (int)(N); i++)
#define RREP(i, N) for (int i = ((int)(N)-1); i >= 0; i--)
#define RREPS(i, N) for (int i = ((int)(N)); i > 0; i--)

#define chmax(ret, x) ret = max(ret, x)
#define chmin(ret, x) ret = min(ret, x)

#define FILL(x, e) memset(x, e, sizeof(x))
#define ZEROS(x) fill(x, 0)

#define UNIQ(x) v.erase(unique(ALL(x)), x.end());

#define BIT(n) (1LL << (n))

#define OUT(x) cout << (x) << "\n"
#define DEBUG(x) cerr << #x << " : " << x << "\n"
#define DEBUG2(x, y) cerr << "(" << #x << ", " << #y << ") = (" << x << ", " << y << ")\n";

#define PB push_back
#define EB emplace_back
#define MP make_pair
#define MT make_tuple
#define FI first
#define SE second

const int MOD = 1e9 + 7;

void iostream_init() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.setf(ios::fixed);
  cout.precision(12);
}

int main() {
  ::iostream_init();

  LL N, K;
  cin >> N >> K;
  vector<LL> X(N, 0);
  vector<LL> A(N, 0);
  REP(i, N) { cin >> X[i]; }
  REP(i, N) { cin >> A[i]; }

  LL Xmin = X[K - 1] - A[K - 1];
  LL Xmax = X[K - 1] + A[K - 1];

  LL ans = 1;

  LL i = K - 1;
  LL j = K - 1;
  while (true) {
    if (i + 1 < N && X[i + 1] <= Xmax) {
      i++;
      Xmin = min(Xmin, X[i] - A[i]);
      Xmax = max(Xmax, X[i] + A[i]);
      ans++;
      continue;
    }

    if (0 <= j - 1 && Xmin <= X[j - 1]) {
      j--;
      Xmin = min(Xmin, X[j] - A[j]);
      Xmax = max(Xmax, X[j] + A[j]);
      ans++;
      continue;
    }
    break;
  }

  cout << ans << endl;
  return 0;
}