#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;
vector<bool> cry;

void dfs(ll idx) {
    if (cry[idx]) return;
    cry[idx] = true;
    auto it = lower_bound(all(x), x[idx] - a[idx]);
    while((it != x.end()) && (*it <= (x[idx] + a[idx]))) {
        dfs(it - x.begin());
        it++;
    }
}

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);
    cry.resize(n, false);
    rep(i, n) cin >> x[i];
    rep(i, n) cin >> a[i];
    dfs(k);
    ll ans = 0;
    rep(i, n) ans += (cry[i] ? 1 : 0);
    cout << ans << endl;
    return 0;
}