#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <cmath>
using namespace std;
using ll = long long;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);

    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];
    }

    int r = 0;
    int i0 = k, i1 = k;
    ll x0 = x[k] - a[k], x1 = x[k] + a[k];
    while (1) {
        while (i0 >= 0 && x[i0] >= x0) {
            x0 = min(x0, x[i0] - a[i0]);
            x1 = max(x1, x[i0] + a[i0]);
            i0--;
        }
        while (i1 < n && x[i1] <= x1) {
            x0 = min(x0, x[i1] - a[i1]);
            x1 = max(x1, x[i1] + a[i1]);
            i1++;
        }
        int t = i1 - i0 - 1;
        if (r == t) break;
        r = t;
    }

    //for (int h = 0; h < 2; h++) {
    //    ll t = 0;
    //    for (int i = k; i + 1 < n && x[i + 1] <= x[i] + a[i]; i++) {
    //        r++;
    //    }
    //    if (h == 1) break;
    //    reverse(x.begin(), x.end());
    //    reverse(a.begin(), a.end());
    //    for (int i = 0; i < n; i++) {
    //        x[i] *= -1;
    //    }
    //    k = n - 1 - k;
    //}

    cout << r << endl;

    return 0;
}