// This is the text editor interface. 
// Anything you type or change here will be seen by the other person in real time.




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

public class Solution {
    
    public static int getMaxLengthPeriod(int[] a,int index){
        int ptr=index;
        while(ptr<a.length-1 && a[ptr+1]-a[index]<=1){
            ptr++;
        }
        return ptr-index+1;
    }
    /**
     * Testing 
     * 1 3 3 4 5 6
     * sorted : 
     **/
    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 result=Integer.MIN_VALUE;
        for(int i=0;i<a.length;i++){
            int period=getMaxLengthPeriod(a,i);
            if(period>result)
                result=period;
        }
        System.out.println(result);
    }
}