#include <bits/stdc++.h>

using namespace std;

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

const double PI = acos(-1);

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  int n, k;
  cin >> n >> k;
  vector<long long> x(n), a(n);
  REP (i, n) cin >> x[i];
  REP (i, n) cin >> a[i];

  --k;
  long long lb = x[k];
  long long ub = x[k];

  for (int i = k; i >= 0; i--) {
    if (x[i] >= lb)
      lb = min(lb, x[i] - a[i]);
  }

  for (int i = k; i < n; i++) {
    if (x[i] <= ub)
      ub = max(ub, x[i] + a[i]);
  }

  int ret = 0;
  REP (i, n) {
    if (lb <= x[i] && x[i] <= ub)
      ++ret;
  }

  cout << ret << endl;
  
  return 0;
}