#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("Yes");}else{puts("No");}
#define MAX_N 200005

int main() {
    int n, k;
    cin >> n >> k;
    ll x[n+2];
    x[0] = -1e18; x[n+1] = 1e18;
    srep(i,1,n+1)cin >> x[i];
    ll a[n+2];
    a[0] = 0; a[n+1] = 0;
    srep(i,1,n+1)cin >> a[i];
    
    int ans = 1;
    ll ma = x[k] + a[k];
    srep(i,k+1,n+1){
        if(ma < x[i])break;
        ans++;
        ma = max(ma, x[i] + a[i]);
    }
    ll mi = x[k] - a[k];
    drep(i,k){
        if(x[i] < mi)break;
        ans++;
        mi = min(mi, x[i] - a[i]);
    }

    cout << ans << endl;
    return 0;
}