#include<iostream>
#include<vector>
#include<cassert>
using namespace std;
typedef long long ll;

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 ld = x[k]-a[k], rd = x[k]+a[k];
    int l = k, r = k;
    bool update = true;

    while(update){
        update = false;
        while(l-1 >= 0 && ld <= x[l-1]){
            update = true;
            l--;
            ld = min(ld, x[l]-a[l]);
            rd = max(rd, x[l]+a[l]);
        }
        while(r+1 < n && x[r+1] <= rd){
            update = true;
            r++;
            rd = max(rd, x[r]+a[r]);
            ld = min(ld, x[r]-a[r]);
        }
    }

    cout << r-l+1 << endl;

    return 0;
}