function toys($w) {
    // Write your code here
    sort($w);
    $count_w = count($w);
    $w_first = $w[0];
    $counter = 1;
    
    for ($i=0; $i < $count_w; $i++) {
        if ($w[$i] > (4 + $w_first)) {
            $counter++;
            $w_first = $w[$i];
        }
    }  
    return $counter;
}

int toys(vector<int> w) {
    sort(w.begin(), w.end());
    int result = 1, mi = w[0];
    for(int item: w){
        if(item > mi + 4){
            mi = item;
            result++;
        }
    }
    return result;
}

import java.util.Arrays;
import java.util.Scanner;

public class Toys {
    public static int toys(int[] w) {
        Arrays.sort(w);
        int total = 1;
        int freeToys = w[0] + 4;
        for (int i = 1; i < w.length; i++) {
            if (w[i] > freeToys) {
                total += 1;
                freeToys = w[i] + 4;
            }
        }
        return total;
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int[] w = new int[n];
        for (int i = 0; i < n; i++) {
            w[i] = scanner.nextInt();
        }
        System.out.println(toys(w));
        scanner.close();
    }
}

#nobara

import math
import os
import random
import re
import sys




def toys(w):
    w.sort()
    total = 1
    free_toys = w[0] + 4
    for i in range(1, len(w)):
        if w[i] > free_toys:
            total += 1
            free_toys = w[i] + 4
    return total

n = int(input().strip())
w = list(map(int, input().strip().split(' ')))
print(toys(w))

def toys(w):
    w.sort()
    total = 1
    free_toys = w[0] + 4
    for i in range(1, len(w)):
        if w[i] > free_toys:
            total += 1
            free_toys = w[i] + 4
    return total

n = int(input().strip())
w = list(map(int, input().strip().split(' ')))
print(toys(w))