#include <iostream>
#include <cstdint>
#include <vector>

using namespace std;

int main()
{
	cin.tie(nullptr);
	ios::sync_with_stdio(false);

	int32_t N, K, i;
	cin >> N >> K;
	vector<int64_t> X(N), A(N);
	for (i = 0; i != N; ++i) cin >> X[i];
	for (i = 0; i != N; ++i) cin >> A[i];

	int64_t l = X[K - 1] - A[K - 1], r = X[K - 1] + A[K - 1];
	int32_t l_i = K - 2, r_i = K;
	while (1)
	{
		if (l_i >= 0 && X[l_i] >= l)
		{
			if (l > X[l_i] - A[l_i]) l = X[l_i] - A[l_i];
			if (r < X[l_i] + A[l_i]) r = X[l_i] + A[l_i];
			--l_i;
			continue;
		}

		if (r_i < N && X[r_i] <= r)
		{
			if (l > X[r_i] - A[r_i]) l = X[r_i] - A[r_i];
			if (r < X[r_i] + A[r_i]) r = X[r_i] + A[r_i];
			++r_i;
			continue;
		}

		break;
	}

	cout << r_i - l_i - 1 << '\n';
	return 0;
}