import java.util.*;
import java.lang.*;
import java.io.*;
import java.math.*;
 
class Solution{
    
	public static void main(String[] args) throws java.lang.Exception{
		// TODO Auto-generated method stub
		
		InputStreamReader r=new InputStreamReader(System.in);  
        BufferedReader br=new BufferedReader(r);
        
        int test=1;
        for(int t=0;t<test;t++)
        {
            int n=Integer.parseInt(br.readLine());
            String s[]=br.readLine().split("\\s");
            long [] array = Arrays.asList(s).stream().mapToLong(Long::parseLong).toArray();
            Arrays.sort(array);
            int count=1;
            for(int j=1;j<n;j++)
            {
                if(array[j]!=array[j-1])
                {
                    count++;
                }
            }
            long unique[]=new long[count];
            int i=1;
            unique[0]=array[0];
            for(int j=1;j<n;j++)
            {
                if(array[j]!=array[j-1])
                {
                    unique[i++]=array[j];
                }
            }
            int freq[]=new int[count];
            for(int j=0;j<n;j++)
            {
                int idx=Arrays.binarySearch(unique,array[j]);
                freq[idx]++;
            }
            int max=freq[0];
            for(int j=0;j<count-1;j++)
            {
                if((unique[j+1]-unique[j]<=1)&&(freq[j]+freq[j+1]>max))
                {
                    max=freq[j]+freq[j+1];
                }
            }
            Arrays.sort(freq);
            if(freq[count-1]>max)
                max=freq[count-1];
            System.out.println(max);
        }
	}
}