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

public class Solution {

	static void solve(int[] a) {
		int[] dist = new int[101];
		for (int i = 0; i < a.length; i++) {
			dist[a[i]]++;
		}
		int result = 0;
		for (int i = 0; i < a.length - 1; i++) {
			int s = dist[i] + dist[i + 1];
			if(s > result) {
				result = s;
			}
		}
		System.out.println(result);
	}

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int[] a = new int[n];
        for(int a_i=0; a_i < n; a_i++){
            a[a_i] = in.nextInt();
        }
        solve(a);
    }
}