#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define rep(i, n) for(ll i = 0, i##_len = (n); i < i##_len; i++)
#define reps(i, s, n) for(ll i = (s), i##_len = (n); i < i##_len; i++)
#define rrep(i, n) for(ll i = (n) - 1; i >= 0; i--)
#define rreps(i, e, n) for(ll i = (n) - 1; i >= (e); i--)
#define all(x) (x).begin(), (x).end()
#define sz(x) ((ll)(x).size())
#define len(x) ((ll)(x).length())

ll n, k;
vector<ll> x, a;
set<pair<ll, ll>> nc;

void dfs(ll v) {
    set<pair<ll, ll>> t;
    ll l = x[v] - a[v], r = x[v] + a[v];
    for(auto it = nc.lower_bound(make_pair(l, LONG_LONG_MIN)); it != nc.end(); ) {
        if (it->first > r) break;
        t.insert(*it);
        nc.erase(it++);
    }
    for(auto te : t) {
        dfs(te.second);
    }
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    // ifstream in("input.txt");
    // cin.rdbuf(in.rdbuf());
    cin >> n >> k;
    k--;
    x.resize(n);
    a.resize(n);
    rep(i, n) cin >> x[i];
    rep(i, n) cin >> a[i];
    rep(i, n) nc.insert(make_pair(x[i], i));
    nc.erase(make_pair(x[k], k));
    dfs(k);
    cout << (n - sz(nc)) << endl;
    return 0;
}