#include<fstream> 
using namespace std; 
ifstream in("zombie.in");
ofstream out("zombie.out");

int main() 
{int d,n,k,v[100005];
int cost=0,suma=0,contor=0,i;
	in>>d>>n>>k; 
	for(i=0;i<n;i++) 
		in>>v[i];
	
	for(i=0;i<n-1;i++) 
		{
			if((v[i+1]-v[i])>=d) 
		cost++; 
		else if((v[i+1]-v[i])<d) 
		{
			if(((v[i+1]-v[i])+suma)<d) 
				{
					suma+=v[i+1]-v[i]; 
					contor++;
			}
			else if((v[i+1]-v[i]+suma)>=d) 
				{
					cost++; 
			if(contor==1) 
				{
					suma=contor=0;
					cost++; 
			}
			else if(contor>1) 
			{
				cost+=k;
				suma=contor=0; 
			}
			}
		}
	}
	if(suma!=0) 
	{
		if(contor==1) cost++; 
		else cost+=k; 
	}
		out<<cost; 
}