// https://yukicoder.me/problems/no/871
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
#define EPS (1e-9)
#define INF (1e9)
#define INFL (1e18)
#define MOD (1000000007)
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define REP(i, n) for (int i = 0; i < (n); ++i)
#define ALL(obj) (obj).begin(), (obj).end()
#define ALLR(obj) (obj).rbegin(), (obj).rend()
#define BIT(n) (1LL << (n))
// ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
// ll lcm(ll c, ll d) { return c / gcd(c, d) * d; }

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    ll n, k;
    cin >> n >> k;
    vector<ll> x(n), a(n);
    REP(i, n) cin >> x[i];
    REP(i, n) cin >> a[i];
    k--;
    ll left = x[k] - a[k], right = x[k] + a[k];
    ll lm = 0, lr = 0;
    while (left != lm || right != lr) {
        lm = left, lr = right;
        for (int i = k; i >= 0; i--) {
            if (left > x[i]) {
                break;
            }
            left = min(left, x[i] - a[i]);
            right = max(right, x[i] + a[i]);
        }
        for (int i = k; i < n; i++) {
            if (right < x[i]) {
                break;
            }
            left = min(left, x[i] - a[i]);
            right = max(right, x[i] + a[i]);
        }
    }
    ll cnt = 0;
    REP(i, n) {
        if (x[i] >= left && x[i] <= right)
            cnt++;
    }
    cout << cnt << endl;

    return 0;
}