/* -*- coding: utf-8 -*-
 *
 * 871.cc:  No.871 かえるのうた - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 100000;

/* typedef */

typedef long long ll;

/* global variables */

ll xs[MAX_N], as[MAX_N];

/* subroutines */

inline void setmin(int &a, int b) { if (a > b) a = b; }
inline void setmax(int &a, int b) { if (a < b) a = b; }

/* main */

int main() {
  int n, k;
  scanf("%d%d", &n, &k);
  k--;

  for (int i = 0; i < n; i++) scanf("%lld", xs + i);
  for (int i = 0; i < n; i++) scanf("%lld", as + i);

  int li = k;
  for (int minli = li; li > 0; li--) {
    setmin(minli, lower_bound(xs, xs + n, xs[li] - as[li]) - xs);
    if (minli == li) break;
  }

  int ri = k + 1;
  for (int maxri = ri; ri < n; ri++) {
    setmax(maxri, upper_bound(xs, xs + n, xs[ri - 1] + as[ri - 1]) - xs);
    if (maxri == ri) break;
  }
  //printf("li=%d, ri=%d\n", li, ri);

  printf("%d\n", ri - li);
  return 0;
}