#pragma region
#pragma GCC target("avx2")
#pragma GCC optimize("03")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
using namespace std; typedef long double ld; typedef long long ll;
typedef unsigned long long ull;
#define endl "\n"
#define FOR(i,a,b) for(int i=(a);i<=(b);i++)
#define rep(i,a,b) for(int i=(a);i<(b);i++)
#define PII pair<int, int>
#define PLL pair<ll, ll>
#define ALL(x) (x).begin(), (x).end()
constexpr int INF=1<<30; constexpr ll LINF=1LL<<60; constexpr ll mod=1e9+7; constexpr int NIL = -1;
template<class T>inline bool chmax(T &a, const T &b) { if (a<b) { a = b; return 1; } return 0; }
template<class T>inline bool chmin(T &a, const T &b) { if (b<a) { a = b; return 1; } return 0; }
#pragma endregion
//-------------------
constexpr int MX = 1e5+5;
ll x[MX];
ll a[MX];

int main(){
    cin.tie(0); ios::sync_with_stdio(false); //cout << fixed << setprecision(15);
    int n,k; cin >> n >> k;
    rep(i,0,n) cin >> x[i];
    rep(i,0,n) cin >> a[i];

    ll left, right;
    k--;
    left = x[k] - a[k];
    right = x[k] + a[k];

    int cnt = 1;
    int r_idx, l_idx;
    r_idx = k + 1;
    l_idx = k -1;
    while(true) {
        bool updated = false;
        if(l_idx >= 0 and x[l_idx] >= left) {
            cnt++;
            chmin(left, x[l_idx]-a[l_idx]);
            chmax(right, x[l_idx] + a[l_idx]);
            updated = true;
            l_idx--;
        }
        if(r_idx < n and x[r_idx] <= right) {
            cnt++;
            chmin(left, x[r_idx]-a[r_idx]);
            chmax(right, x[r_idx]+a[r_idx]);
            updated = true;
            r_idx++;
        }
        if(!updated) break;
    }


    cout << cnt << endl;
    return 0;
}