#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;
     
     
}