import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;
import java.util.Set;

public class Solution {

	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		HashMap<Integer, Integer> map = new HashMap<>();
		int[] arr = new int[n];
		for(int i=0;i<n;i++){
			arr[i] = scan.nextInt();
			if(!map.containsKey(arr[i])){
				map.put(arr[i],1);
			}
			else{
				int val = map.get(arr[i]);
				val++;
				map.put(arr[i], val);
			}
		}
		Set<Map.Entry<Integer, Integer>> allEntries = map.entrySet();
		int ans = 0;
		for(Map.Entry<Integer, Integer> entry : allEntries){
			int num = entry.getKey();
			int max = 0;
			if(map.get(num-1)!=null && map.get(num-1)>0){
				max = map.get(num-1);
				
			}
            max += entry.getValue();
			if(max > ans){
				ans = max;
			}
		}
		System.out.println(ans);

	}

}