#include <iostream>
#include <iomanip>
#include <cstdio>
#include <queue>
#include <cstring>
#include <vector>
#include <map>
#include <algorithm>
#include <cctype>
#include <cmath>
#include <bitset>
#include <set>
#include <stack>
using namespace std;

#define REP(i,n) for(int i=0;i<(int)(n);i++)
#define RREP(i,n) for(int i=n-1;i>=0;i--)
#define FOR(i,k,n) for(int i=(k);i<(int)(n);i++)
#define all(i,n) (i),(i+n)

int dx4[4]={1,0,-1,0};
int dy4[4]={0,-1,0,1};
int dx8[8]={1,0,-1,1,-1,1,0,-1};
int dy8[8]={1,1,1,0,0,-1,-1,-1};
int dx9[9]={0,1,0,-1,1,-1,1,0,-1};
int dy9[9]={0,1,1,1,0,0,-1,-1,-1};

typedef pair<int, int> P;
typedef pair<string, int> SP;
typedef long long ll;
typedef pair<ll, ll> PLL;

const int INF = 1e9;
const ll LLINF = 1e18;
const int MAX_V = 1e6+1;
const ll mod = 1000000007;
// << fixed << setprecision
// --------------------------------------
int n, k;
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);

  cin >> n >> k;
  vector<ll> x(n + 1, 0);
  vector<ll> a(n + 1, 0);

  REP(i, n) cin >> x[i + 1];
  REP(i, n) cin >> a[i + 1];
  int l = k, r = k;
  ll ld = x[k] - a[k];
  ll rd = x[k] + a[k];
  bool update = true;

  while(update) {
    update = false;
    while(l - 1 >= 1 && ld <= x[l - 1]) {
      update = true;
      l--;
      ld = min(ld, x[l] - a[l]);
      rd = max(rd, x[l] + a[l]);
    }

    while(r + 1 <= n && x[r + 1] <= rd) {
      update = true;
      r++;
      ld = min(ld, x[r] - a[r]);
      rd = max(rd, x[r] + a[r]);
    }
  }

  cout << (r - l + 1) << endl;
}