/*

This Submission is to determine how many 120/240 min const. delivery point there are.

//info
120 req. steps <= 5
*/
#define  _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <algorithm>
#include <utility>
#include <functional>
#include <cstring>
#include <queue>
#include <stack>
#include <math.h>
#include <iterator>
#include <vector>
#include <string>
#include <set>
#include <math.h>
#include <iostream>
#include <random>
#include<map>
#include <iomanip>
#include <time.h>
#include <stdlib.h>
#include <list>
#include <typeinfo>
#include <list>
#include <set>
#include <cassert>
#include<fstream>
#include <unordered_map>
#include <cstdlib>
#include <complex>
#include <cctype>
#include <bitset>
using namespace std;
typedef string::const_iterator State;
#define Ma_PI 3.141592653589793
#define eps 0.00000001
#define LONG_INF 1e18
#define GOLD 1.61803398874989484820458
#define MAX_MOD 1000000007
#define MOD 1000000007
#define seg_size 262144
#define REP(a,b) for(long long a = 0;a < b;++a)

unsigned long xor128() {
	static unsigned long x = time(NULL), y = 362436069, z = 521288629, w = 88675123;
	unsigned long t = (x ^ (x << 11));
	x = y; y = z; z = w;
	return (w = (w ^ (w >> 19)) ^ (t ^ (t >> 8)));
}
int main() {
#define int long long
	int n, k;
	cin >> n >> k;
	vector<pair<long long, long long>> inputs;
	REP(i, n) {
		long long a;
		cin >> a;
		inputs.push_back(make_pair(a, 0));
	}
	REP(i, n) {
		cin >> inputs[i].second;
	}
	k--;
	int ans = 1;
	long long bot = inputs[k].first - inputs[k].second;
	for (int i = k - 1; i >= 0; --i) {
		if (bot > inputs[i].first) {
			break;
		}
		ans++;
		bot = min(bot, inputs[i].first - inputs[i].second);
	}
	bot = inputs[k].first + inputs[k].second;
	for (int i = k + 1; i < n; ++i) {
		if (inputs[i].first > bot) {
			break;
		}
		ans++;
		bot = max(bot, inputs[i].first + inputs[i].second);
	}
	cout << ans << endl;
	return 0;
}