#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(n);++i)
#define all(a) (a).begin(),(a).end()
#define dunk(a) cout << (a) << endl
using namespace std;
typedef long long ll;

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	int n, k;
	cin >> n >> k;
	vector<ll> x(n);
	vector<ll> a(n);
	rep(i, n) cin >> x[i];
	rep(i, n) cin >> a[i];
	k--;

	ll r = x[k] + a[k];//right
	ll l = x[k] - a[k];//left
	bool elf = true;
	int b = k;
	int c = k;

	while (elf) {
		elf = false;
		if (b - 1 >= 0) {
			ll i = b - 1;
			if (l <= x[i] && x[i] <= r) {
				b = i;
				l = min(l, x[i] - a[i]);
				r = max(r, x[i] + a[i]);

				elf = true;
				continue;
			}
		}
		if (c + 1 <= n - 1) {
			ll i = c + 1;
			if (l <= x[i] && x[i] <= r) {
				c = i;
				l = min(l, x[i] - a[i]);
				r = max(r, x[i] + a[i]);

				elf = true;
				continue;
			}
		}
	}
	ll ans = c - b + 1;
	dunk(ans);

	return 0;
}