#include<fstream>
#include<algorithm>
#include<map>
using namespace std;

ifstream in("zombie.in");
ofstream out("zombie.out");

int N, K, D;

int A[1000010];

int main()
{
	in >> D >>N>>K;

	for (int i = 1;i <= N;++i)
		in >> A[i];
	int S=0,nr=1,p=1;
	for (int i = 2;i <= N;++i)
	{
		if (D - (A[i] - A[p]) <= 1)
		{
			if (nr < K)
			{
				++S;
				++p;
				--nr;
			}
			else
			{
				p += nr;
				S += K;
				nr = 1;
			}
		}
		else
			++nr;
	}
	if (N == 1)
		++S;
	else
	{
		if (nr < K)
		{
			++S;
			++p;
		}
		else
		{
			p += nr;
			S += K;
		}
	}
	
	out << S;

	return 0;
}