#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
int main() {
    int N, K;
    cin >> N >> K;
    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];
    }
    K--;
    ll r = X[K] + A[K];
    ll l = X[K] - A[K];
    int idr = K + 1;
    int idl = K - 1;
    int cnt = 1;
    while (idr < N || idl >= 0) {
        if (idr < N && X[idr] <= r) {
            r = max(r, X[idr] + A[idr]);
            l = min(l, X[idr] - A[idr]);
            cnt++;
            idr++;
        } else if (idl >= 0 && l <= X[idl]) {
            r = max(r, X[idl] + A[idl]);
            l = min(l, X[idl] - A[idl]);
            cnt++;
            //cout << idl << "\n";
            idl--;
        } else {
            break;
        }
    }
    //cout << l << " " << r << "\n";
    cout << cnt << "\n";
  return 0;
}