using System;
using System.Text;

namespace RandomAz {
    static class Program {
        static char GetRandomCharAz(Random rand) {
            // (('Z' - 'A' + 1) << 1) == 52
            int v = rand.Next(52);
            return (char)(((v >> 1) + 'A') | ((v & 1) << 5));
        }
        static string GetRandomStringAz(int length, Random rand) {
            StringBuilder sb = new StringBuilder();
            while(--length >= 0)
                sb.Append(GetRandomCharAz(rand));
            return sb.ToString();
        }
        static void Main(string[] args) {
            Random rand = new Random();
            Console.WriteLine(GetRandomStringAz(64, rand));
        }
    }
}