#include <bits/stdc++.h>
#define Int int64_t

using namespace std;

int main() {
	int N, K;
	cin >> N >> K;
	vector<Int> x(N + 1), a(N + 1);
	for (int i = 1; i <= N; ++i) { cin >> x[i]; }
	for (int i = 1; i <= N; ++i) { cin >> a[i]; }

	int kl = K, kr = K;
	Int xl = x[K] - a[K], xr = x[K] + a[K];
	bool update = false;
	while (true) {
		update = false;
		while (kl - 1 > 0) {
			if (x[kl - 1] < xl || x[kl - 1] > xr) { break; }
			--kl;
			xl = min(xl, x[kl] - a[kl]);
			xr = max(xr, x[kl] + a[kl]);
			update = true;
		}
		while (kr < N) {
			if (x[kr + 1] < xl || x[kr + 1] > xr) { break; }
			++kr;
			xl = min(xl, x[kr] - a[kr]);
			xr = max(xr, x[kr] - a[kr]);
			update = true;
		}
		if (!update) { break; }
	}
	cout << kr - kl + 1 << endl;

	return 0;
}