#include <bits/stdc++.h>
using namespace std;
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) begin(v),end(v)
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
using ll = long long;
using pii = pair<int, int>;
constexpr ll INF = 1ll<<30;
constexpr ll longINF = 1ll<<60;
constexpr ll MOD = 1000000007;
constexpr bool debug = false;
//---------------------------------//

int main() {
	int N, K;
	cin >> N >> K; --K;
	vector<ll> X(N), A(N);
	REP(i, N) scanf("%lld", &X[i]);
	REP(i, N) scanf("%lld", &A[i]);
	int l = K, r = K;
	queue<int> que;
	que.emplace(K);
	while (!que.empty()) {
		int u = que.front(); que.pop();
		while (r + 1 < N && abs(X[r + 1] - X[u]) <= A[u]) que.emplace(++r);
		while (l - 1 >= 0 && abs(X[l - 1] - X[u]) <= A[u]) que.emplace(--l);
	}
	cout << r - l + 1 << endl;
}