#include<bits/stdc++.h>
using namespace std;
#define ALL(x) x.begin(),x.end()
#define rep(i,n) for(int i=0;i<(n);i++)
#define debug(v) cout<<#v<<":";for(auto x:v){cout<<x<<' ';}cout<<endl;
#define INF 1000000000
#define mod 1000000007
using ll=long long;
const ll LINF=1001002003004005006ll;
int dx[]={1,0,-1,0};
int dy[]={0,1,0,-1};
// ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
template<class T>bool chmax(T &a,const T &b){if(a<b){a=b;return true;}return false;}
template<class T>bool chmin(T &a,const T &b){if(b<a){a=b;return true;}return false;}

signed main(){
    cin.tie(0);
    ios::sync_with_stdio(0);
    
    int n,k;cin>>n>>k;k--;
    ll x[n],a[n];
    rep(i,n) cin>>x[i];
    rep(i,n) cin>>a[i];

    int l,r;
    ll lmin=x[k];
    for(l=k;l>=0;l--){
        if(x[l]>=lmin) ;
        else break;
        chmin(lmin,x[l]-a[l]);
    }
    ll rmax=x[k];
    for(r=k;r<n;r++){
        if(x[r]<=rmax) ;
        else break;
        chmax(rmax,x[r]+a[r]);
    }
    cout<<r-l-1<<endl;
    return 0;
}