// yukicoder: 871 かえるのうた
// 2019.8.30 bal4u

#include <stdio.h>
#include <string.h>

typedef long long ll;

//// 高速入力
#if 1
#define gc() getchar_unlocked()
#else
#define gc() getchar()
#endif

ll in()   // 整数の入力（負数対応）
{
	ll n = 0; int c = gc();
	if (c == '-') {	c = gc();
		do n = 10*n + (c & 0xf), c = gc(); while (c >= '0');
		return -n;
	}
	do n = 10*n + (c & 0xf), c = gc(); while (c >= '0');
	return n;
}

#define MAX 100005
int q[MAX], top;
ll  X[MAX], R[MAX], L[MAX]; int N;
char f[MAX];

int main()
{
	int i, l, r, x, K, ans; ll a, ma, mi;
	
	N = (int)in(), K = (int)in()-1;
	memset(f, 1, N);
	for (i = 0; i < N; i++) X[i] = in();
	for (i = 0; i < N; i++) a = in(), R[i] = X[i]+a, L[i] = X[i]-a;
	
	top = 0, q[top++] = K, f[K] = 0;
	while (top) {
		i = q[--top];
		
		a = ma = R[i], r = i-1, x = i;
		while (++r < N && X[r] <= a) if (f[r]) {
			f[r] = 0;
			if (ma < R[r]) ma = R[r], x = r;
		}
		if (x != i) q[top++] = x;
		
		a = mi = L[i], l = i+1, x = i;
		while (--l >= 0 && X[l] >= a) if (f[l]) {
			f[l] = 0;
			if (mi > L[l]) mi = L[l], x = l;
		}
		if (x != i) q[top++] = x;
	}
	ans = 0; for (i = 0; i < N; i++) if (!f[i]) ans++;
	printf("%d\n", ans);
	return 0;
}