#include<fstream>
#include<algorithm>
   
   
#define NMAX 1000002
using namespace std;
   
  
ifstream f("zombie.in");
ofstream g("zombie.out");
  
int d,n,k;
  
int dist[NMAX];
int res[NMAX];
int limit;
  
void read ( void )
{
    f>>d>>n>>k;
      
    limit=1;
    for(int i(1); i <= n ; ++i )
    {
        f>>dist[i];
          
        res[i]=res[i-1]+1;
          
        while( dist[limit] < dist[i] - ( d-1 )  )
              ++limit;
        res[i]=min( res[i] , res[limit-1]+k )   ;
    }  
          
    f.close();
}
   
   
void write ( void )
{
       
    g<<res[n];
    g.close();
}
   
   
int main()
{
    read();
      
    write();
    return 0;
       
       
}