#include<iostream>
#include<algorithm>
#include<vector>
using namespace std;
int main() {
	int n, d;
	cin >> n >> d;
	int *arr = new int[n];
	for (int i = 0; i < n; i++) {
		cin >> arr[i];
	}
	sort(arr, arr + n);
	int cnt = (arr[n - 1] - arr[0]) / d;
	if (cnt*d != (arr[n - 1] - arr[0])) {
		cnt++;
	}
	cnt--;
	if (n == 1||n==2) {
		cout << 0;
		return 0;
	}
	cout << n - cnt - 2;
}