using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Numerics;

namespace yukicoder
{
    class Program
    {
        const int intMax = 1000000000;
        const long longMax = 2000000000000000000;
        static void Main(string[] args)
        {
            int N = int.Parse(Console.ReadLine());
            var A = Console.ReadLine().Split().Select(int.Parse).ToArray();
            var dp = new long[N + 1, 10];
            var modA = A.Select(p => p % 10).ToArray();
            dp[0, 0] = 0;
            for(int i = 1; i <= N; i++)
            {
                for(int j = 0; j < 10; j++)
                {
                    if((i == 1 && j == 0) || dp[i - 1,j] > 0)
                    {
                        dp[i, (j + modA[i - 1]) % 10] = Math.Max(dp[i - 1, j] + 1, dp[i, (j + modA[i - 1]) % 10]);
                        if(i + 1 <= N)
                        {
                            dp[i + 1, (j + modA[i - 1]) % 10] = Math.Max(dp[i + 1, (j + modA[i - 1]) % 10],dp[i, (j + modA[i - 1]) % 10]);
                        }
                    }
                    if(i + 1 <= N)
                    {
                        dp[i + 1, j] = Math.Max(dp[i + 1,j],dp[i,j]);
                    }             
                    
                }
            }
            Console.WriteLine(dp[N, 0]);
        }
    }
}