#include<stdio.h>
int main()
{
	int n, k;
	scanf("%d %d", &n, &k);
	k--;
	int i, j;
	long long int x[100005], a[100005];
	for (i = 0; i < n; i++)
		scanf("%lld", &x[i]);
	for (i = 0; i < n; i++)
		scanf("%lld", &a[i]);
	int ans = 1;
	long long int left, right;
	i = j = k;
	left = x[k] - a[k];
	right = x[k] + a[k];
	for (;;)
	{
		if (i > 0)
		{
			if (left <= x[i - 1])
			{
				ans++;
				i--;
				if (left > x[i] - a[i])
					left = x[i] - a[i];
				if (right < x[i] + a[i])
					right = x[i] + a[i];
				continue;
			}
		}
		if (j < n - 1)
		{
			if (x[j + 1] <= right)
			{
				ans++;
				j++;
				if (left > x[j] - a[j])
					left = x[j] - a[j];
				if (right < x[j] + a[j])
					right = x[j] + a[j];
				continue;
			}
		}
		break;
	}
	printf("%d\n", ans);
	return 0;
}