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

public class Solution {
    public static int max(int a, int b){
        if(a>b){
            return a;
        }
        else{
            return b;
        }
    }
    public static int[] sort(int[] a,int n){
        int t=1;
        while(t!=0){
            t=0;
            for(int i=0;i<n-1;i++){
                if(a[i]>a[i+1]){
                    t++;
                    int temp=a[i];
                    a[i]=a[i+1];
                    a[i+1]=temp;
                }
            }
        }
        return a;
        
    }

    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();
        }
        int[] b=new int[n];
        b=sort(a,n);
        int ans=0;
        for(int i=0;i<n-1;i++){
            int t=0,j=i,k=b[i];
            while(j<n&&b[j]-b[i]<2){
                t++;
                j++;
            }
            ans=max(ans,t);
            
        }
        System.out.println(ans);
    }
}