#include <algorithm>
#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rrep(i, n) for (int i = (int)n - 1; i > -1; i--)
#define all(x) (x).begin(), (x).end()
#define ll long long
#define ld long double
#define INF 1000000000000000000
typedef pair<ll, ll> pll;

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

    int N, K;
    cin >> N >> K;
    K--;
    vector<ll> X(N), A(N);
    vector<pll> kukan(N);
    rep(i, N) { cin >> X[i]; }

    rep(i, N) { cin >> A[i]; }

    rep(i, N) {
        kukan[i].first = X[i] - A[i];
        kukan[i].second = X[i] + A[i];
    }

    ll l = kukan[K].first, r = kukan[K].second;
    int right = K + 1, left = K - 1;
    int cnt = 1;
    while (right < N || left > -1) {
        if (right < N && X[right] <= r) {
            r = max(r, kukan[right].second);
            l = min(l, kukan[right].first);
            cnt++;
            right++;
        } else if (left >= 0 && l <= X[left]) {
            r = max(r, kukan[left].second);
            l = min(l, kukan[left].first);
            cnt++;
            left--;
        } else
            break;
    }

    cout << cnt << endl;
}