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

public class Solution {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
		int n = scanner.nextInt();
		ArrayList<Integer> l = new ArrayList<>();
		ArrayList<Integer> listOfNumbers = new ArrayList<>();
		ArrayList<Integer> occuranceForTheNumber = new ArrayList<>();

		for (int i = 0; i < n; i++) {
			int num = scanner.nextInt();
			l.add(num);
		}
		Collections.sort(l);

		for (int i = 0; i < n; i++) {
			int num = l.get(i).intValue();
			if (!listOfNumbers.contains((Integer) num)) {
				listOfNumbers.add(num);
				occuranceForTheNumber.add(0);
			}
			int index = listOfNumbers.indexOf((Integer) num);
			occuranceForTheNumber.set(index, occuranceForTheNumber.get(index) + 1);
		}

		int maxPossibleNumber = 0;
		int currentPossibleNumber;
		for (int i = 0; i < listOfNumbers.size() - 1; i++) {
			int diff = listOfNumbers.get(i + 1).intValue() - listOfNumbers.get(i).intValue();
			diff = (diff < 0) ? (-1 * diff) : diff;
			if (diff <= 1) {
				currentPossibleNumber = occuranceForTheNumber.get(i) + occuranceForTheNumber.get(i + 1);
			} else {
				currentPossibleNumber = occuranceForTheNumber.get(i);
			}
			maxPossibleNumber = (maxPossibleNumber < currentPossibleNumber) ? currentPossibleNumber : maxPossibleNumber;
		}
		currentPossibleNumber = occuranceForTheNumber.get(listOfNumbers.size() - 1);
		maxPossibleNumber = (maxPossibleNumber < currentPossibleNumber) ? currentPossibleNumber : maxPossibleNumber;

//		System.out.println(listOfNumbers);
//		System.out.println(occuranceForTheNumber);
		System.out.println(maxPossibleNumber);
    }
}