#include <algorithm>
#include <stdio.h>
#include <iostream>
#include <fstream>

#define MAX 1000010

using namespace std;

int n, d, k;
int sol[MAX], a[MAX];

int main()
{
	ifstream cin("zombie.in");
	ofstream cout("zombie.out");

	cin >> d >> n >> k;

	for (int i = 1; i <= n; i++)
		cin >> a[i];

	int pr = 0;
	for (int i = 1; i <= n; i++)
	{
		for (; a[pr + 1] <= a[i] - d; pr++);

		sol[i] = min(sol[pr] + k, sol[i - 1] + 1);
	}

	cout << sol[n];

	return 0;
}