class Program
{
    static void Main(string[] args)
    {
        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();
        
        for (int i = 0; i < numList.Count - 1; i++)
        {
            if (numList[i] + 1 != numList[i + 1])
            {
                Console.WriteLine("No");
                return;
            }
        }

        Console.WriteLine("Yes");
    }
}