//package hack101_44;

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

/**
 *
 * link to problem:
 * https://www.hackerrank.com/contests/101hack44/challenges/picking-numbers
 */
public class A {

    int n;
    List<Integer> list = new ArrayList<>();
    int[] arr = new int[101];

    public static void main(String[] args) {
        new A().solve();
    }

    private void solve() {
        Scanner in = new Scanner(System.in);
        n = in.nextInt();

        for (int i = 0; i < n; i++) {
            int val = in.nextInt();
            list.add(val);
            arr[val]++;
        }

        int maxSum = 0;
        for (int i = 0; i + 1 < arr.length; i++) {
            int a = arr[i];
            int b = arr[i + 1];
            int sum = a + b;
//            System.out.println("a=" + a);
//            System.out.println("b=" + b);
//            System.out.println("s=" + sum);

            if (sum > maxSum) {
                maxSum = sum;
            }
        }
        System.out.println(maxSum);
    }

}