#include <bits/stdc++.h>
using namespace std;
int main(void){
    cin.tie(0);
    ios::sync_with_stdio(false);

    int N; cin >> N;
    int K; cin >> K;
    K -= 1;
    vector<long long> X(N);
    set<pair<long long, int>> s;
    for (int i = 0; i < N; i++) {
        cin >> X[i];
        if (i != K) s.insert({X[i], i});
    }
    vector<pair<long long, long long>> interval(N);
    for (int i = 0; i < N; i++) {
        long long A; cin >> A;
        interval[i] = {X[i] - A, X[i] + A};
    }
    
    stack<pair<long long, long long>> st;
    st.push(interval[K]);
    while (!st.empty()) {
        pair<long long, long long> p = st.top();
        st.pop();
        auto itr = s.lower_bound({p.first, 0});
        while (itr != s.end() && itr->first <= p.second) {
            st.push(interval[itr->second]);
            s.erase(itr++);
        }
    }
    
    cout << N - s.size() << endl;
    return 0;
}