using namespace std;
#include<cstdio>
#define MAX 1000005
int v[MAX];
int main()
{
	freopen("zombie.in","r",stdin);
	freopen("zombie.out","w",stdout);
	int n,d,k,cost=0,j,i;
	scanf("%d %d %d",&d,&n,&k);
	for(i=1;i<=n;i++)
		scanf("%d",&v[i]);
	for(i=1;i<=n;i++)
	{
		j=i;
		for(;(v[i]-v[j]<d)&&(i<=n);i++);
		if(i-j>=k)
			cost+=k;
		else
			cost+=i-j;
	}
	printf("%d\n",cost);
	return 0;
}