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 k=0;
        int max=0, maxI=0;;
        for(int a_i=0; a_i < n; a_i++){
            a[a_i] = in.nextInt();
            if(a[a_i]>max)
            max =a[a_i];

            
        }
        List<Integer> iList = new ArrayList<>();

        for (int i : a) {
            iList.add(i);
        }
        
        int iCount=0;
            
        for(int i=1;i<=max;i++){
        iCount = Collections.frequency(iList, i);
        if(Collections.frequency(iList, i-1)>0)
            iCount=iCount + Collections.frequency(iList, i-1);
        
        //System.out.println(i+ " " + iCount);
        if(iCount>maxI)
            maxI=iCount;
        }
        
        
        
            //for(int j=0;i<n;j++){
               // if(Math.abs(a[i]-a[j])<=1)
             
            //}
            
        //System.out.println("maxI");
        System.out.println(maxI);
    }
}