from base64 import b64decode, b64encode


def decode(s: str) -> bytes:
    s = b64decode(s + "=" * (-len(s) % 4), "-_")
    r = b""

    assert s[-1] == 2

    i = 0
    while i < len(s) - 1:
        if s[i] != 0:
            r += bytes([s[i]])
        else:
            r += b"\x00" * s[i + 1]
            i += 1

        i += 1

    return r


def encode(s: bytes) -> str:
    r = b""
    n = 0

    for i in s + bytes([2]):
        if i == 0:
            n += 1
        else:
            if n:
                r += b"\x00" + bytes([n])
                n = 0

            r += bytes([i])

    return b64encode(r, b"-_").decode().rstrip("=")