#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;
    for(int i=k-1;i>=0;i--) {
        if(x[i] >= left) {
            cnt++;
            chmin(left, x[i]-a[i]);
        }
        else break;
    }

    rep(i,k+1, n) {
        if(x[i] <= right) {
            cnt ++;
            chmax(right, x[i]+a[i]);
        }
        else break;
    }

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