#include <bits/stdc++.h>

using namespace std;

using ll = long long;

void solve(int cur, int& L, int& R, vector<ll>& x, vector<ll>& a) {
    int li = lower_bound(x.begin(), x.end(), x[cur] - a[cur]) - x.begin();
    int ri = upper_bound(x.begin(), x.end(), x[cur] + a[cur]) - x.begin();

    int nL = L;
    if (li < L) nL = li;

    int nR = R;
    if (ri > R) nR = ri;

    vector<int> ids;
    for (int i = li; i < ri; ) {
        if (i >= L && i < R) {
            i = R;
            continue;
        }

        ids.push_back(i);
        i++;
    }

    L = nL;
    R = nR;
    for (int i : ids) {
        solve(i, L, R, x, a);
    }
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int n, K;
    cin >> n >> K;
    K--;
    vector<ll> x(n);
    for (int i = 0; i < n; i++) cin >> x[i];

    vector<ll> a(n);
    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }

    int L = K;
    int R = K + 1;
    solve(K, L, R, x, a);
    cout << R - L << endl;
    return 0;
}