#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdint.h>
#include <math.h>

void main() {
	int num_of_req, reqs_per_sec;
	int index = 0;
	int current_requests = 1;
	int* timestamps;

	if(scanf("%d %d", &num_of_req, &reqs_per_sec) == 2) {
	}
	timestamps = (int*)malloc(num_of_req * sizeof(int));

	if(scanf("%d", &timestamps[0]) == 1) {
	}

	for (int i = 1; i < num_of_req; i++) {
		if (scanf("%d", &timestamps[i]) == 1) {
		}

		if (timestamps[index] <= timestamps[i] - 1000){
			index++;
		}
		else {
			current_requests++;
		}
	}
	float servers_required = ceil((float)current_requests / (float)reqs_per_sec);
	printf("%d", (int)servers_required);
}