#include<cstdio>
using namespace std;
int nr[1000010],sol[1000010];
int D,N,K;
inline int minim(int a,int b){
	return a<b?a:b;
}
int main(){
	freopen("zombie.in","r",stdin);
	freopen("zombie.out","w",stdout);
	int i,j;
	scanf("%d%d%d",&D,&N,&K);
	for(j=i=1;i<=N;++i){
		scanf("%d",&nr[i]);
		while(nr[i]-nr[j]>=D)
			++j;
		sol[i]=minim(sol[j-1]+K,sol[i-1]+1);
	}
	printf("%d\n",sol[N]);
	fclose(stdin);
	fclose(stdout);
	return 0;
}