#include <algorithm>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <functional>
#include <iostream>
#include <map>
#include <memory>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>
 
using namespace std;
 
typedef long long ll;
 
#define sz size()
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define all(c) (c).begin(), (c).end()
#define rep(i,a,b) for(ll i=(a);i<(b);++i)
#define per(i,a,b) for(ll i=b-1LL;i>=(a);--i)
#define clr(a, b) memset((a), (b) ,sizeof(a))
#define ctos(c) string(1,c)
#define print(x) cout<<#x<<" = "<<x<<endl;
 
#define MOD 1000000007

vector<int> uf, usz;
int nc;

void init(int n){
  vector<int> uf_(n);
  vector<int> usz_(n, 1);
  uf = uf_;
  usz = usz_;
  nc = n;

  for(int i = 0; i < uf.size(); i++){
    uf[i] = i;
  }
}

int find(int a){
  return (uf[a] == a) ? a : uf[a] = find(uf[a]);
}

void union_(int a, int b){
  a = find(a);
  b = find(b);

  if(a != b){
    if(usz[a] >= usz[b]){
      swap(a, b);
    }
    uf[a] = b;
    usz[b] += usz[a];
    nc--;
  }
}

int check(int a, int b){
  return (find(a) == find(b)) ? 1 : 0;
}

int get_size(int a){
  return usz[find(a)];
}

int main() {
	ll n,k;
	cin>>n>>k;
	k--;
	vector<ll> vx,va;
	rep(i,0,n){
		ll a;
		cin>>a;
		vx.pb(a);
	}
	rep(i,0,n){
		ll a;
		cin>>a;
		va.pb(a);
	}
	ll ans1 = 0;
	ll ans2 = 0;
	ll mx = vx[k]+va[k];
	rep(i,k+1,n){
		if(vx[i]<=mx)ans1++;
		else break;
		mx = max(mx,vx[i]+va[i]);
	}
	ll mn = vx[k]-va[k];
	per(i,0,k){
		if(mn<=vx[i])ans2++;
		else break;
		mn = min(mn,vx[i]-va[i]);
	}
	cout << ans1+ans2+1 << endl;
	return 0;
}