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

int main(){
    int N;
    int K;
    cin>>N>>K;
    K-=1;

    long long X[N];
    long long A[N];

    for (int i=0;i<N;i+=1){
        cin>>X[i];
    }
    for (int i=0;i<N;i+=1){
        cin>>A[i];
    }

    long long PLUS=X[K]+A[K];
    long long MINUS=X[K]-A[K];
    int ANS[N];
    ANS[K]=1;

    for (int roop=0;roop<100;roop+=1){

        for (int i=0;i<N;i+=1){
            if (X[i]<=PLUS && X[i]>=MINUS){
                ANS[i]=1;
                PLUS=max(PLUS,X[i]+A[i]);
                MINUS=min(MINUS,X[i]-A[i]);
            }
        }

        for (int i=N-1;i>=0;i-=1){
            if (X[i]<=PLUS && X[i]>=MINUS){
                ANS[i]=1;
                PLUS=max(PLUS,X[i]+A[i]);
                MINUS=min(MINUS,X[i]-A[i]);
            }
        }

    }
    int AW=0;
    for (int i=0;i<N;i+=1){
        if (ANS[i]==1){
            AW+=1;
        }
    }

    cout<<AW<<endl;
}