internal class Program
{
    private static void Main(string[] args)
    {
        List<string> names = new List<string>();

        string s = Console.ReadLine();
        int Count = int.Parse(s);
        for (int i = 0; i < Count; i++)
        {
            string[] nameInput = Console.ReadLine().Split(' ');
            names.Add(nameInput[0]);
            names.Add(nameInput[1]);
        }

        if (names.Distinct().Count() < names.Count)
        {
            Console.WriteLine("No");
        }
        else
        {
            Console.WriteLine("Yes");
        }
    }
}