class Program {
        private static byte[] Magiya(int chislo) {
            Debug.Assert(chislo >= 0, "Eeee, blyat!");
            if(chislo == 0) {
                return new byte[] {0x30};
            }
            var i = (int) Math.Ceiling(Math.Log10(chislo + 1));
            var otvet = new byte[i];
            while(chislo != 0) {
                i -= 1;
                otvet[i] = (byte)(0x30 + chislo % 10);
                chislo /= 10;
            }
            return otvet;
        }

        static void Main(string[] args) {
            using(var fs = new FileStream("text.txt", FileMode.Create, FileAccess.Write))
            using(var bw = new BinaryWriter(fs)) {
                Random rnd = new Random();

                for(uint i = 0; i < 10000; i++) {
                    bw.Write(Magiya(rnd.Next(0, 10000)));
                    bw.Write((byte) 0x20);
                }
            }
            System.Diagnostics.Process.Start("text.txt");
        }
    }