#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=1;

    for (int i=K+1;i<N;i+=1){
        if (X[i]<=PLUS){
            ANS+=1;
            PLUS=max(PLUS,X[i]+A[i]);
        }
    }

    for (int i=K-1;i>=0;i-=1){
        if (X[i]>=MINUS){
            ANS+=1;
            MINUS=min(MINUS,X[i]-A[i]);
        }
    }

    cout<<ANS<<endl;
}