//include
//------------------------------------------
#include <vector>
#include <list>
#include <map>
#include <unordered_map>
#include <climits>
#include <set>
#include <unordered_set>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>
#include <queue>
#include <random>
#include <complex>
#include <regex>
#include <locale>
#include <random>
#include <type_traits>

using namespace std;

#define SHOW_VECTOR(v) {std::cerr << #v << "\t:";for(const auto& xxx : v){std::cerr << xxx << " ";}std::cerr << "\n";}
#define SHOW_MAP(v){std::cerr << #v << endl; for(const auto& xxx: v){std::cerr << xxx.first << " " << xxx.second << "\n";}}

using LL = long long;

//------------------------------------------
//------------------------------------------

typedef tuple<LL, LL, LL> TT;

int main() {

    LL 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];

    vector<bool> used(N, false);

    used[K] = true;
    queue<TT> Q;
    Q.push(make_tuple(K, X[K] - A[K], X[K] + A[K]));

    while (!Q.empty()) {
        LL id, ld, rd;
        tie(id, ld, rd) = Q.front();
        Q.pop();
        auto left_it = lower_bound(X.begin(), X.end(), ld);
        auto right_it = upper_bound(X.begin(), X.end(), rd);
        while (left_it != right_it) {
            LL to = left_it - X.begin();
            if (!used[to]) {
                used[to] = true;
                Q.push(make_tuple(to, X[to] - A[to], X[to] + A[to]));
            }
            left_it++;
        }
    }

    LL ans = count(used.begin(), used.end(), true);
    cout << ans << endl;

}