//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;

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

int main() {

    int N, K;
    cin >> N >> K;
    K--;

    vector<LL> X(N), A(N);
    for (int i = 0; i < N; i++) cin >> X[i];
    for (int i = 0; i < N; i++) cin >> A[i];

    LL lk = K;
    LL rk = K;

    LL ld = X[lk] - A[lk];
    LL rd = X[rk] + A[rk];

    bool update = false;
    while (true) {
        update = false;
        while (lk - 1 >= 0 && ld <= X[lk - 1]) {
            lk--;
            ld = min(ld, X[lk] - A[lk]);
            rd = max(rd, X[lk] + A[lk]);
            update = true;
        }
        while (rk + 1 <= N - 1 && rd >= X[rk + 1]) {
            rk++;
            ld = min(ld, X[rk] - A[rk]);
            rd = max(rd, X[rk] + A[rk]);
            update = true;
        }
        if (!update) break;
    }

    cout << rk - lk + 1 << endl;

}