import static java.lang.Math.abs;
import java.util.Arrays;
import java.util.Scanner;
public class PickingNumber {
    public static void main(String[] args) {
        Scanner ob=new Scanner(System.in);
        int n=ob.nextInt();
        int arr[]= new int[n];
        int count=0;
        for(int i=0;i<n;i++){
            arr[i]=ob.nextInt();
        }
        int max=0;
        Arrays.sort(arr);
        for(int i=0;i<n-1;i++){
            count=0;
            for(int j=i+1;j<n;j++){
                if(abs(arr[i]-arr[j])<=1){
                    count++;
                }
                else{
                    count=0;
                }
                if(max<=count){
                    max=count;
                }
            }
        }
            System.out.println(max+1);
        
    }
}