import java.util.Scanner;
import java.util.Arrays;
public class Solution {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] a = new int[n];
        for(int i=0; i < n; i++){
            a[i] = sc.nextInt();
        }
        Arrays.sort(a);
        int c,j,max=0;
        for(int i=0;i<n;i++){
            c=0;
            for(j=i;j<n && a[j]-a[i]<2;j++)
                c++;
            if(c>max)
                max=c;
        }
        System.out.println(max);
    }
}