#include<bits/stdc++.h>
using namespace std;

#define rep(i,n) for(ll i=0;i<(n);++i)
using ll = long long;
using pll = pair<ll,ll>;
constexpr ll INF = (1LL<<60);
constexpr ll MOD = (1e9+7);
//constexpr ll MOD = (998244353);
template<class T> bool chmax(T &a,const T &b){if(a<b){a=b;return 1;}return 0;}
template<class T> bool chmin(T &a,const T &b){if(a>b){a=b;return 1;}return 0;}
void dump(){cout<<endl;}
template<class T,class... Ts> void dump(T&& h, Ts&&... t){cout<<h<<", ";dump(forward<Ts>(t)...);}
template<class T> istream &operator>>(istream&is,vector<T>&v){for(auto &elemnt:v)is>>elemnt;return is;}
template<class T,class U> istream &operator>>(istream&is,pair<T,U>&p){is>>p.first>>p.second;return is;}
template<class T>vector<T> make_vector(size_t a){return vector<T>(a);}
template<class T, class... Ts>auto make_vector(size_t a, Ts... ts){return vector<decltype(make_vector<T>(ts...))>(a, make_vector<T>(ts...));}
void solve1();
main(){solve1();}

template<class T>
class segtree {
private:
  ll n=1;
  T unit;
  std::vector<T> dat;
  std::function<T(T,T)> func;
public:
  segtree(){}
  segtree(std::vector<T>& a,T v,std::function<T(T,T)> f){
    build(a,v,f);
  }
  void build(std::vector<T>& a,T v,std::function<T(T,T)> f){
    ll sz=a.size();
    unit=v;
    func=f;
    while(n<sz)n<<=1LL;
    dat.resize(2*n-1,unit);
    for(int i=0;i<sz;++i)dat[i+n-1]=a[i];
    for(int i=n-2;i>=0;--i){
      dat[i]=func(dat[i*2+1],dat[i*2+2]);
    }
  }
  void update(ll idx,T val){
    idx+=n-1;
    dat[idx]=val;
    while(idx){
      idx--;idx>>=1LL;
      dat[idx]=func(dat[idx*2+1],dat[idx*2+2]);
    }
  }
  T query(ll a,ll b,ll k=0,ll l=0,ll r=-1){
    if(r<0)r=n;
    if( b<=l || r<=a )return unit;
    if( a<=l && r<=b )return dat[k];
    else{
      auto left=query(a,b,2*k+1,l,(l+r)/2);
      auto right=query(a,b,2*k+2,(l+r)/2,r);
      return func(left,right);
    }
  }
};


void solve1(){

  ll n,k;
  cin>>n>>k;
  k--;
  vector<ll> x(n),a(n);
  cin>>x>>a;

  vector<pll> left(n),right(n);
  rep(i,n){
    left[i].first=x[i]+a[i];
    right[i].first=x[i]-a[i];
    left[i].second=right[i].second=i;
  }

  segtree<pll> leftmax(left,pll(-INF,-INF),[](auto a,auto b){return max(a,b);});
  segtree<pll> rightmin(right,pll(INF,INF),[](auto a,auto b){return min(a,b);});

  ll low=k,high=k;
  vector<bool> seen(n,false);
  queue<ll> que;
  que.emplace(k);
  while(!que.empty()){
    ll i = que.front();
    que.pop();
    if(seen[i])continue;
    seen[i]=true;
    auto litr = upper_bound(x.begin(),x.end(),left[i].first);
    litr--;
    ll lidx = litr-x.begin();
    chmax(high,lidx);
    pll lm = leftmax.query(i,lidx+1);
    que.emplace(lm.second);
    auto ritr = lower_bound(x.begin(),x.end(),right[i].first);
    ll ridx = ritr-x.begin();
    chmin(low,ridx);
    pll rm = rightmin.query(ridx,i+1);
    que.emplace(rm.second);
  }

  cout<<(high-low+1)<<endl;

}