using namespace std;
#include<iostream>
#include<fstream>

ifstream f("zombie.in");
ofstream g("zombie.out");

int n,d,k;
int dp[1000050];
int timp[1000050];

int main()
{
	int i;
	f>>d>>n>>k;
	int distanta=1;
	for(i=1; i<=n; i++)
	{
		f>>timp[i];

		dp[i]=dp[i-1]+1;

        while( timp[distanta] < timp[i] -(d-1) )
			++distanta;
		dp[i]=min( dp[i] , dp[distanta-1]+k );

	}
	g<<dp[n];
}