#include <bits/stdc++.h>
#define whlie while
#define pb push_back
#define eb emplace_back
#define fi first
#define se second
#define rep(i,N) for(int i = 0; i < (N); i++)
#define repr(i,N) for(int i = (N) - 1; i >= 0; i--)
#define rep1(i,N) for(int i = 1; i <= (N) ; i++)
#define repr1(i,N) for(int i = (N) ; i > 0 ; i--)
#define each(x,v) for(auto& x : v)
#define all(v) (v).begin(),(v).end()
#define sz(v) ((int)(v).size())
#define vrep(v,it) for(auto it = v.begin(); it != v.end(); it++)
#define vrepr(v,it) for(auto it = v.rbegin(); it != v.rend(); it++)
#define ini(...) int __VA_ARGS__; in(__VA_ARGS__)
#define inl(...) ll __VA_ARGS__; in(__VA_ARGS__)
#define ins(...) string __VA_ARGS__; in(__VA_ARGS__)
#define rand rng
using namespace std; void solve();
using ll = long long;
using vi = vector<int>;
using vl = vector<ll>;
using vvi = vector< vector<int> >;
constexpr int inf = 1001001001;
constexpr ll infLL = (1LL << 61) - 1;
mt19937_64 rng(58);
struct IoSetupNya {IoSetupNya() { cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(15); cerr << fixed << setprecision(7);} } iosetupnya;
template<typename T, typename U> inline bool amin(T &x, U y) { return (y < x) ? (x = y, true) : false; }
template<typename T, typename U> inline bool amax(T &x, U y) { return (x < y) ? (x = y, true) : false; }
template<typename T, typename U> ostream& operator <<(ostream& os, const pair<T, U> &p) { os << p.first << " " << p.second; return os; }
template<typename T, typename U> istream& operator >>(istream& is, pair<T, U> &p) { is >> p.first >> p.second; return is; }
template<typename T> ostream& operator <<(ostream& os, const vector<T> &v) { int s = (int)v.size(); rep(i,s) os << (i ? " " : "") << v[i]; return os; }
template<typename T> istream& operator >>(istream& is, vector<T> &v) { for(auto &x : v) is >> x; return is; }
void in(){} template <typename T,class... U> void in(T &t,U &...u){ cin >> t; in(u...);}
void out(){cout << "\n";} template <typename T,class... U> void out(const T &t,const U &...u){ cout << t; if(sizeof...(u)) cout << " "; out(u...);}
template<typename T>void die(T x){out(x); exit(0);}
#ifdef NyaanDebug
  #include "NyaanDebug.h"
  #define trc(...) do { cerr << #__VA_ARGS__ << " = "; dbg_out(__VA_ARGS__);} while(0)
  #define trca(v,N) do { cerr << #v << " = "; array_out(v , N);cout << endl;} while(0)
  int main(){solve_dbg();}
#else
  #define trc(...)
  #define trca(...)
  int main(){solve();}
#endif

using P = pair<ll,ll>;
constexpr int MOD = 998244853;

/////////
void solve(){
  ini(N , K); K--;

  vl x(N); in(x);
  vl a(N); in(a);

  vi flg(N , 0);
  flg[K] = 1;

  ll maxx = x[K] + a[K] , minx = x[K] - a[K];
  
  rep( hoge , 1000 ){
  rep(i , N){
    if(minx <= x[i] && x[i] <= maxx){
      flg[i] = 1;
      minx = min(minx , x[i] - a[i]);
      maxx = max(minx , x[i] + a[i]);
    }
  }
  repr(i , N){
    if(minx <= x[i] && x[i] <= maxx){
      flg[i] = 1;
      minx = min(minx , x[i] - a[i]);
      maxx = max(minx , x[i] + a[i]);
    }
  }
  }

  int ans = 0;
  rep(i , N) ans += flg[i];
  out(ans);
}