pub fn sn_to_level0nth(sn: u64) -> u64 {
let (high, low) = (sn / 2048, sn % 2048);
high * 2048 * 2 + low
}
pub fn level0nth_to_level8nth(level0nth: u64) -> u64 {
let twig_id = level0nth / (2 * 2048);
8 * 2 * twig_id + 8 + ((level0nth / 256) % 8)
}
pub fn sn_to_level8nth(sn: u64) -> u64 {
let level0nth = sn_to_level0nth(sn);
level0nth_to_level8nth(level0nth)
}