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 in = new Scanner(System.in);
		int n = in.nextInt();
		int[] a = new int[103];
		int max = 0, maxAdjacent = 0, val = 0;
		while (n-- > 0) {
			val = in.nextInt() + 1;
			a[val]++;
			if ((max + maxAdjacent) < (a[val] + Math.max(a[val + 1] , a[val - 1]))) {
				max = a[val];
				maxAdjacent= Math.max(a[val + 1] , a[val - 1]);
			}
		}
		System.out.println(max + maxAdjacent );

	}
}