#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define F first
#define S second
#define pii pair<int, int>
#define eb emplace_back
#define all(v) v.begin(), v.end()
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep3(i, l, n) for (int i = l; i < (n); ++i)
#define sz(v) (int)v.size()
#define inf (int)(1e9+7)
#define abs(x) (x >= 0 ? x : -(x))
#define ceil(a, b) a / b + !!(a % b)
ll pow(ll a, int b) { return b ? pow(a * a, b / 2) * (b % 2 ? a : 1) : 1; }
template<typename T> T gcd(T a, T b) { if (b == 0) return a; return gcd(b, a % b); }


int main() {
    int n, k;
    cin >> n >> k;
    k--;
    vector<ll> x(n), a(n);
    rep(i, n) cin >> x[i];
    rep(i, n) cin >> a[i];
    
    
    ll l = x[k] - a[k], r = x[k] + a[k];
    // cout << l << " " << r << endl;
    
    int cnt[100001] = {0};
    cnt[k] = 1;
    for (int i = k - 1; i >= 0; --i) {
        if (l <= x[i] && x[i] <= r) {
            
            cnt[i] = 1;
            l = min(l, x[i] - a[i]);
            r = max(r, x[i] + a[i]);
        } else {
            break;
        }
    }
    
    rep3(i, k + 1, n) {
        if (l <= x[i] && x[i] <= r) {
            cnt[i] = 1;
            l = min(l, x[i] - a[i]);
            r = max(r, x[i] + a[i]);
        } else {
            break;
        }
    }
    
    for (int i = k - 1; i >= 0; --i) {
        if (l <= x[i] && x[i] <= r) {
            cnt[i] = 1;
            l = min(l, x[i] - a[i]);
            r = max(r, x[i] + a[i]);
        } else {
            break;
        }
    }
    
    rep3(i, 1, 100001) cnt[i] += cnt[i - 1];
    cout << cnt[10000] << endl;
}