import java.util.Arrays;
import java.util.Scanner;

public class Solution {

    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();
        }
        Arrays.sort(a);

        int count = 1;
        int lastIncrement = 0;
        int max = 0;
        for(int i = 1; i < n; i++) {
            if ((a[i] == a[i-1])||(a[i]-a[i-1] == 1 && Math.abs(a[lastIncrement]-a[i]) <= 1)) {
                count++;
            } else {
                max = max < count ? count : max;
                if (Math.abs(a[i]-a[i-1]) <= 1) {
                    count = i - lastIncrement;
                } else {
                    count = 1;
                }
            }
            if (a[i] != a[i-1]) {
                lastIncrement = i - 1;
            }
        }
        max = max < count ? count : max;
        System.out.println(max);
    }
}