#include <iostream>
using namespace std;
int n,p[1000010],d,sp[100000010],ans;
int main()
{
cin>>n>>d;
for (int i=1;i<=n;i++)
cin>>p[i],sp[p[i]]=1;
int j=1;
for (int i=0;j<=n;j++)
i=p[j];
for (int k=i+1;k<=i+d;k++)
if (sp[k]==1)
ans++;
cout<<ans;
return 0;
}