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


signed main(){
    ios::sync_with_stdio(false);
	cin.tie(0);

    ll n,k;
    cin>>n>>k;
    k--;
    ll x[n],a[n];
    for(int i=0;i<n;i++){
        cin>>x[i];
    }
    for(int i=0;i<n;i++){
        cin>>a[i];
    }
    ll r=k,l=k,up=x[k]+a[k],low=x[k]-a[k];
    while(true){
        ll pr=r,pl=l;
        while(r<n && up>=x[r]){
            up = max(x[r]+a[r],up);
            low = min(low,x[r]-a[r]);
            r++;
        }
        while(l>=0 && low<=x[l]){
            up = max(up,x[l] + a[l]);
            low = min(low, x[l]-a[l]);
            l--;
        }
        if(pr==r && pl==l) break;
    }
    // cerr<<l<<" "<<r<<endl;
    // cerr<<low<<" "<<up<<endl;
    cout << r-l-1 << endl;
}