#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];
    for (int i = K + 1; i < N; i++) {
        if (X[i] <= r) {
            r = max(r, X[i] + A[i]);
            l = min(l, X[i] - A[i]);
        } else {
            break;
        }
    }
    for (int i = K - 1; i >= 0; i--) {
        if (l <= X[i]) {
            r = max(r, X[i] + A[i]);
            l = min(l, X[i] - A[i]);
        } else {
            break;
        }
    }
    int cnt = 0;
    for (int i = 0; i < N; i++) {
        if ((l <= X[i] && X[i] <= X[K]) ||(X[K] <= X[i] && X[i] <= r)) {
            cnt++;
        }
    }
    //cout << l << " " << r << "\n";
    cout << cnt << "\n";
  return 0;
}