#include <bits/stdc++.h>
#define rep(i, a, n) for(int i = a; i < n; i++)
#define int long long
using namespace std;
typedef pair<int, int> P;
const int mod = 1000000007;
const int INF = 1e18;

signed main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int n, k;
    cin >> n >> k;
    vector<P> d(n);
    rep(i, 0, n) cin >> d[i].first;
    rep(i, 0, n) cin >> d[i].second;
    k--;
    int r = d[k].first + d[k].second;
    int l = d[k].first - d[k].second;
    int rid = k + 1, lid = k - 1;
    for(int i = 0; i < n; i++){
        while(rid < n && d[rid].first <= r){
            r = max(r, d[rid].first + d[rid].second);
            l = min(l, d[rid].first - d[rid].second);
            rid++;
        }
        while(lid >= 0 && d[lid].first >= l){
            r = max(r, d[lid].first + d[lid].second);
            l = min(l, d[lid].first - d[lid].second);
            lid--;
        }
    }
    int ans = 0;
    rep(i, 0, n) if(l <= d[i].first && d[i].first <= r) ans++;
    cout << ans << endl;
}