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 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[] c = new int[100];
        for ( int i = 0; i < n; i++ )
        {
            c[a[i] - 1]++;
            c[a[i]]++;
        }
        int max = 0;
        for ( int i = 0; i < 100; i++ )
            max = Math.max( max, c[i] );
        System.out.println( max );
    }
}