#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define P pair<ll,ll>
#define FOR(I,A,B) for(ll I = ll(A); I < ll(B); ++I)
#define FORR(I,A,B) for(ll I = ll((B)-1); I >= ll(A); --I)
#define TO(x,t,f) ((x)?(t):(f))
#define SORT(x) (sort(x.begin(),x.end())) // 0 2 2 3 4 5 8 9
#define POSL(x,v) (lower_bound(x.begin(),x.end(),v)-x.begin()) //xi>=v  x is sorted
#define POSU(x,v) (upper_bound(x.begin(),x.end(),v)-x.begin()) //xi>v  x is sorted
#define NUM(x,v) (POSU(x,v)-POSL(x,v))  //x is sorted
#define REV(x) (reverse(x.begin(),x.end())) //reverse
ll gcd(ll a,ll b){if(a%b==0)return b;return gcd(b,a%b);}
ll lcm(ll a,ll b){ll c=gcd(a,b);return ((a/c)*(b/c)*c);}
#define NEXTP(x) next_permutation(x.begin(),x.end())
const ll INF=ll(1e18)+ll(7);
const ll MOD=1000000007LL;
#define out(a) cout<<fixed<<setprecision((a))




int main(){
	ll N,K;
	cin >> N >> K;
	K--;
	ll ans = 0;
	set<ll> setX;
	map<ll,ll> indexX;
	vector<ll> A(N),X(N);
	FOR(i,0,N){
		cin >> X[i];
		if(i!=K)setX.insert(X[i]);
		indexX[X[i]] = i;
	}
	FOR(i,0,N)cin >> A[i];



	queue<ll> nex;
	vector<bool> did(N,0);
	nex.push(K);
	did[K] = true;
	while(nex.size()){
		ans++;
		ll nowi = nex.front();
		nex.pop();
		ll nowX = X[nowi];
		ll nowA = A[nowi];
		vector<ll> usedX;
		auto it = setX.upper_bound(nowX-nowA-1LL);
		auto la = setX.upper_bound(nowX+nowA);
		while(it != la){
			ll XXX = *it;
			nex.push(indexX[XXX]);
			usedX.push_back(XXX);
			++it;
		}
		for(auto xxx:usedX){
			setX.erase(xxx);
		}
	}
	cout << ans << endl;
}