#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];
    }

    int right = K, left = K;
    while (right < N - 1) {
        ll tar = kukan[right].second;
        ll cur = upper_bound(all(X), tar) - X.begin() - 1;
        if (cur == right)
            break;
        right = cur;
    }

    while (left > 0) {
        ll tar = kukan[left].first;
        ll cur = lower_bound(all(X), tar) - X.begin();
        if (cur == left)
            break;
        left = cur;
    }

    cout << right - left + 1 << endl;
}