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 scanner = new Scanner(System.in);
		
		int t;
		
		t = scanner.nextInt();
		HashMap<Integer, Integer> map= new HashMap<>();
		int[] n = new int[t];

		for(int i = 0; i<t; i++){
			int x  = scanner.nextInt();
			if(map.containsKey(x)){
				map.put(x, map.get(x)+1);
			}
			else
				map.put(x, 1);
		}
		int c = 0;
		for(int i = 0; i < 100;i++){
			int cTemp = 0;

			if(map.containsKey(i))
				cTemp += map.get(i);

			if(map.containsKey(i+1))
				cTemp += map.get(i+1);

			
			if(cTemp>c){
				c=cTemp;
			}
		}
		System.out.println(c);

	}

}