#include <bits/stdc++.h>


using namespace std;
typedef long long ll;
#define REP(i,n) for(int i=0; i<int(n); i++)
#define FOR(i,m,n) for(int i=int(m); i<int(n); i++)
#define ALL(obj) (obj).begin(),(obj).end()
#define VI vector<int>
#define VLL vector<long long>
#define VVI vector<vector<int>>
#define VVLL vector<vector<long long>>
#define VC vector<char>
#define VS vector<string>
#define VVC vector<vector<char>>
#define VB vector<bool>
#define VVB vector<vector<bool>>
#define fore(i,a) for(auto &i:a)

typedef pair <int, int> P;
template<class T> bool chmax(T &a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> bool chmin(T &a, T b) { if (a > b) { a = b; return true; } return false; }
const int  INF = 1 << 29;
const ll INFL = 1LL << 60;
const ll mod = 1000000007;





int main() {
	

	int n, k;
	cin >> n >> k;
	VLL x(n), a(n);
	REP(i, n)cin >> x[i];
	REP(i, n)cin >> a[i];
	k--;
	ll b = x[k] + a[k];
	ll c = x[k] - a[k];
	int r = k;
	int l = k;
	while (true) {
		int check = r - l;
		while (r < n - 1) {
			if (x[r + 1] <= b) {
				r++;
				b = max(b, x[r] + a[r]);
				c = min(c, x[r] - a[r]);
			}
			else break;
		}
		while (0 < l) {
			if (x[l - 1] >= c) {
				l--;
				c = min(c, x[l] - a[l]);
				b = max(b, x[l] + a[l]);
			}
			else break;
		}
		if (check == r - l)break;
	}
	cout << r - l + 1 << endl;
	

}