#include <stdio.h>
#include <string>
#include <cstring>
#include <stdlib.h>
#include <math.h>
#include <algorithm>
#include <vector>
#include <set>
#include <map>
#include <queue>
#include <list>
#include <iterator>
#include <assert.h>
#pragma warning(disable:4996) 
 
typedef long long ll;
#define MIN(a, b) ((a)>(b)? (b): (a))
#define MAX(a, b) ((a)<(b)? (b): (a))
#define LINF 9223300000000000000
#define INF 2140000000
const long long MOD = 1000000007;
using namespace std;




int main(int argc, char* argv[])
{
    int n,k;
    scanf("%d%d", &n, &k);

    vector<ll> x(n),a(n);
    int i;
    for(i=0; i<n; i++) {
        scanf("%lld", &x[i]);
    }
    for(i=0; i<n; i++) {
        scanf("%lld", &a[i]);
    }
    
    vector<ll> maxval, minval, xval, xval2;
    for(i=k-1; i<n; i++) {
        if(i==k-1) { maxval.push_back(x[i]+a[i]); xval.push_back(0); }
        else       { maxval.push_back(MAX(maxval.back(),x[i]+a[i])); xval.push_back(x[i]-x[k-1]); }
    }
    for(i=k-1; i>=0; i--) {
        if(i==k-1) { minval.push_back(a[i]-x[i]); xval2.push_back(0); }
        else       { minval.push_back(MAX(minval.back(),a[i]-x[i])); xval2.push_back(x[k-1]-x[i]); }
    }

    int mini=0, maxi=0;
    for(i=0; i<n; i++) {
        maxi=lower_bound(xval.begin(), xval.end(), maxval[mini]+1)-xval.begin()-1;
        mini=lower_bound(xval2.begin(), xval2.end(), minval[mini]+1)-xval2.begin()-1;
    }
    printf("%d\n", maxi+mini+1);

    return 0;
}