#include <fstream>
#include <algorithm>

#define DIM 1000005

using namespace std;

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

int n, D, k;

int dp[DIM], v[DIM];

int main() {

	fin >> D >> n >> k;

	int pos = 1;

	for (int i = 1; i <= n; i++) {

		fin >> v[i];

		while (pos <= i && v[i] - v[pos] >= D)
			pos++;

		dp[i] = min(dp[i - 1] + 1, dp[pos - 1] + k);

	}

	fout << dp[n];

	return 0;

}

//Trust me, I'm the Doctor!
//Miriam e tare!