public void Compress()
{
string s = input.ReadString();
int N = s.Length;
output.Write(N);
// Write two-bit code for char.
for (int i = 0; i < N; i++)
{
int d = Alphabet.Dna.ToIndex(s[i]);
output.Write(d, 2);
}
output.Close();
input.Close();
}
