#include<stdio.h>
#include<queue>
using namespace std;
queue <int> q;
int main()
{
	freopen("zombie.in","r",stdin);
	freopen("zombie.out","w",stdout);
	int d,n,k,x,zombie=0,chakra=0,add,i;
	scanf("%d%d%d",&d,&n,&k);
	for(i=1;i<=n;i++)
	{
		scanf("%d",&x);
		q.push(x+d);
	}
	while(!q.empty())
	{
		add=q.front()-1;
		while(!q.empty()&&q.front()-add<=d)
		{
			zombie++;
			q.pop();
		}
		if(zombie>=k)
			chakra+=k;
		else
			chakra+=zombie;
		zombie=0;
	}
	printf("%d\n",chakra);
	return 0;
}