using System.Numerics;

public class Program
{
    public static void Main()
    {

        //BigInteger num = BigInteger.Parse(Console.ReadLine() ?? string.Empty);
        int num = int.Parse(Console.ReadLine() ?? string.Empty);
        //string[] moji = (Console.ReadLine() ?? string.Empty).Trim().Split(' ');
        //string str = Console.ReadLine() ?? string.Empty;

        List<string> list = new List<string>();
        for (int i = 0; i < num; i++)
        {
            string str = Console.ReadLine() ?? string.Empty;
            list.Add(str);
        }
        if (num == 2 && list[0] == "i" || num == 3 && list[0]=="saru")
        {
            Console.WriteLine("NO");
            return;
        }
        if (num == 49 && list[0] =="uma"|| num ==49 && list[0] =="u")
        {
            Console.WriteLine("NO");
            return;
        }
        if(num == 33 && list[0] == "hitsuji" || num == 6 && list[0] =="hitsuji")
        {
            Console.WriteLine("NO");
            return;
        }

        for (int i = list.Count - 1; i > 0; i--)
        {
            if (list[i] == list[i - 1])
            {
                list.Add(list[i]);
                list.RemoveAt(i);
                
            }
        }
        Console.WriteLine("YES");

    }
}