public static int toys(List<Integer> w) {
        System.out.println(w);
        Collections.sort(w);
        int containers = 1;
        int tempLimit = w.get(0);
        for (int i = 1; i < w.size(); i++) {
            if (w.get(i) > tempLimit+4) {
                tempLimit = w.get(i);
                containers++;
            }

        }
        return containers;
    }

public static int toys(List<int> w)
    {
        w.Sort();
        var result = 0;
        
        for(int i = 0; i< w.Count;)
        {
            var currMax = w[i] + 4;
            while(i < w.Count && w[i] <= currMax)
            {
                i++;
            }
            result++;
        }
        
        return result;
    }

public static int toys(List<int> w)
{
	var containerCount = 1;
	w.Sort();
	var minWeight = w[0];
	
	for (var i = 0; i < w.Count; i++)
	{
		if (w[i] - minWeight <= 4)
			continue;
		containerCount++;
		minWeight = w[i];
	}
	
	return containerCount;
}

import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.regex.*;

class Result {

    /*
     * Complete the 'toys' function below.
     *
     * The function is expected to return an INTEGER.
     * The function accepts INTEGER_ARRAY w as parameter.
     */

    public static int toys(List<Integer> w) {
    // Write your code here
        int c=1;
        int j=0;
        Collections.sort(w);
        for(int i=1;i<w.size();i++){
            if(w.get(i)-w.get(j)>=5){
                c++;
                j=i;
                System.out.println(j);
            }
        }
return c;
    }

}

public class Solution {
    public static void main(String[] args) throws IOException {
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(System.getenv("OUTPUT_PATH")));

        int n = Integer.parseInt(bufferedReader.readLine().trim());

        String[] wTemp = bufferedReader.readLine().replaceAll("\\s+$", "").split(" ");

        List<Integer> w = new ArrayList<>();

        for (int i = 0; i < n; i++) {
            int wItem = Integer.parseInt(wTemp[i]);
            w.add(wItem);
        }

        int result = Result.toys(w);

        bufferedWriter.write(String.valueOf(result));
        bufferedWriter.newLine();

        bufferedReader.close();
        bufferedWriter.close();
    }
}