#define _USE_MATH_DEFINES
#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define MT make_tuple
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
#define RT return
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;
using vll = vector<ll>;

void solve() {
    int N, K;
    cin >> N >> K;
    --K;
    vll X(N), A(N);

    rep(i, N)cin >> X[i];
    rep(i, N)cin >> A[i];

    map<ll, ll> xa;
    rep(i, N) {
        if (i != K)xa[X[i]] = A[i];
    }

    ll ub = X[K] + A[K], lb = X[K] - A[K];
    while (true) {
        auto it = xa.lower_bound(lb);
        if (it != xa.end() && it->first <= ub) {
            smax(ub, it->first + it->second);
            smin(lb, it->first - it->second);
            xa.erase(it);
        } else {
            break;
        }
    }

    int ans = N - sz(xa);
    cout << ans << endl;
}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout << fixed << setprecision(15);
	solve();
	return 0;
}