class Program
{
    static void Main(string[] args)
    {
        int total = int.Parse(Console.ReadLine()!);
        string[] input = Console.ReadLine()!.Split(' ');
        List<int> numList = new List<int>();

        for (int i = 0; i < input.Length; i++)
        {
            numList.Add(int.Parse(input[i]));
        }
        numList.Sort();

        int sum = 0;
        for (int i = 0;i < numList.Count; i++)
        {
            if (i == 0 || numList[i] - 1 != numList[i - 1])
            {
                sum += numList[i];
            }
        }

        Console.WriteLine(sum);
    }
}