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[n];
        int hash[] = new int[101];
        int max1=00;
        for(int a_i=0; a_i < n; a_i++){
            a[a_i] = in.nextInt();
            hash[a[a_i]]++;
            if(max1 < a[a_i]){
                max1 = a[a_i];
            }
        }
        /*for(int i=1;i<=n;i++){
            for(int j=0;j<=n-i-1;j++){
                if(a[j]>a[j+1]){
                    int temp = a[j];
                    a[j] = a[j+1];
                    a[j+1] = temp;
                }
            }
        }*/
        int max=0;
        for(int i=1;i<max1;i++){
            int d = hash[i]+hash[i+1];
            if(max<=d){
                max = d;
            }
        }
        /*for(int i=0;i<n;i++){
            int count=0;
            int b[] = new int[n];
            //b[0] = a[0];
            int k=0;
            for(int j=i;j<n-1;j++){
                if(Math.abs(a[j]-a[j+1]) <=1 && j == i){
                    b[k++] = a[j];
                    b[k++] = a[j+1];
                    count++;
                }
                else if(Math.abs(a[j]-a[j+1]) <=1){
                    b[k++] = a[j];
                    b[k++] = a[j+1];
                    count++;
                }
                else{
                    break;
                }
            }
            if(max<count){
                max = count;
            }
        }*/
        System.out.println(max);
    }
}