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


int main(){
    ll N, K; cin>>N>>K;
    ll X[N], A[N];
    for(int i=1;i<=N;i++) cin>>X[i];
    for(int i=1;i<=N;i++) cin>>A[i];

    ll ans = 1;
    ll l=X[K]-A[K];
    ll r=X[K]+A[K];
    ll p = K-1; //2
    ll q = K+1; //4
    while((l <= X[p] || X[q] <= r) && 0 < p && q <= N ){
        if(l <= X[p]){
            ans++;
        }
        if(X[q] <= r){
            ans++;
        }
        l = min(X[p]-A[p], X[q]-A[q]);
        r = max(X[p]+A[p], X[q]+A[q]);
        cout<<"l="<<l<<endl;
        cout<<"r="<<r<<endl;
        p--;
        q++;
    }
    cout<<ans<<endl;
}