#include<cstdio>
#define minim(a,b) a<b?a:b
void read(),solve();
int n,k,i,st,A[1000010],cost[1000010],d;
int main()
{
	read();
	solve();
	return 0;
}
void read()
{
	freopen("zombie.in","r",stdin);
	freopen("zombie.out","w",stdout);
	scanf("%d%d%d",&d,&n,&k);
}
void solve()
{
	st=1;
	for(i=1;i<=n;i++)
	{
		scanf("%d",&A[i]);
		while(A[st]+d<A[i])st++;
		cost[i]=minim(cost[i-1]+1,cost[st-1]+k);
	}
	printf("%d\n",cost[n]);
}