#include<stdio.h>
#include<algorithm>
using namespace std;
int din[1010100];
int v[1010100];
int D,N,cost;

int main()
{
freopen("zombie.in","r",stdin);
freopen("zombie.out","w",stdout);
    scanf("%d%d%d",&D,&N,&cost);
    for(int i=1;i<=N;++i)
        scanf("%d",&v[i]);
    int mij=1;
    for(int i=1;i<=N;++i)
    {
    while(!(v[mij]+D>=v[i]))
    ++mij;
     //  printf("%d\n",caut(v[i],i));
        din[i]=min(din[i-1]+1,din[mij-1]+cost);
        //printf(" %d\n",caut(v[i],i));
    }
    printf("%d",din[N]);

}