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

public class Solution {

    
    /*
    
    Examples
    
    a.
    4 6 5 3 3 1
    
    6 5 4 3 3 1
    ___________
    6 5,
    5 4,
    4 3 3
    3 3
    1
    
    
    b.
    1 2 2 3 1 2
    
    
    Pseudo
    
    sort arr
    
    sum
    count
    
        maxCount = 0;
        while index is bigger than -1

            if(element at index differs from start element by more than 1)
            {
                get value of previous index
                get first occurence index of that value 
                set index to that 

                if(sum > maxSum){
                    maxCount = count
                    maxSum
                }
            }

            increase sum
            increase count
            if next element has difference of 1 and nextStartIndex hasn't been set
                start iteration from nextStartIndex
    
    */
    
    //6 5 4 3 3 1
    //1 2 2 3 1 2
    //1 1 2 2 2 3
    static int maxSum(int[] arr){
        
        Arrays.sort(arr);

        int maxCount = -1;
        int count = 0;
        
        boolean nextIndexNotSet = true;
        int nextIndex = -1;
        int index = arr.length-1;
        int value = arr[index];
        while(index > -1){
            
            if(value != arr[index] && nextIndexNotSet){
                nextIndex = index;
                nextIndexNotSet = false;
            }
            
            if(value - arr[index] < 2){
                count++;
                index--;
            }else{
                if(count > maxCount){
                    maxCount = count;
                }
                index = nextIndex;
                count = 0;
                value = arr[index];
                nextIndexNotSet = true;
            }
            
        }
        
        if(count > maxCount){
            maxCount = count;
        }
        
        return maxCount;
    }
    
    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();
        }
        
        System.out.println(maxSum(a));
    }
}