#include <bits/stdc++.h>
#define rep(i, a, n) for(int i = a; i < n; i++)
#define int long long
using namespace std;
typedef pair<int, int> P;
const int mod = 1000000007;
const int INF = 1e18;

signed main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int n, k;
    cin >> n >> k;
    vector<P> d(n);
    rep(i, 0, n) cin >> d[i].first;
    rep(i, 0, n) cin >> d[i].second;
    int preX = d[k - 1].first;
    sort(d.begin(), d.end());
    k = lower_bound(d.begin(), d.end(), P{preX, 0}) - d.begin();
    int r = d[k].first + d[k].second;
    int l = d[k].first - d[k].second;
    int ans = 0;
    rep(i, k + 1, n){
        if(d[i].first <= r){
            r = max(r, d[i].first + d[i].second);
            l = min(l, d[i].first - d[i].second);
        }
    }
    for(int i = k - 1; i >= 0; i--){
        if(d[i].first >= l){
            r = max(r, d[i].first + d[i].second);
            l = min(l, d[i].first - d[i].second);
        }
    }
    rep(i, 0, n) if(l <= d[i].first && d[i].second <= r) ans++;
    cout << ans << endl;
}