#include<fstream>
using namespace std;

#define nmax 1000002

long long D,x[nmax];
int N,K,s,timp;

int main()
{
	ifstream f("zombie.in");
	ofstream g("zombie.out");
	
	f>>D>>N>>K;
	
	for(int i=1;i<=N;i++)
		f>>x[i];
	
	int timp=0;
	
	for(int i=1;i<N;i++)
	{
		timp=timp+x[i+1]-x[i];
		
		int t=i;
			if(timp<D)
			{
			while(timp<D && t<N)
			{
				t++;
				timp=timp+x[i+1]-x[i];
			}
				t--;
					if(t-i+1>K) s=s+K;
				else s=s+t-i+1;
			i=t;
			}
			else
			{
				timp=0;
				s++;
			}
	}
	g<<s;
}