# Collatz sequence optimized: single-pass parity/half and gated odd branch
PRINT X

# Build C = 300 using 10*10*3
CLEAR A
INCREASE A INCREASE A INCREASE A INCREASE A INCREASE A INCREASE A INCREASE A INCREASE A INCREASE A INCREASE A
CLEAR B
REPEAT A TIMES (
    REPEAT A TIMES (
        INCREASE B
    )
)
CLEAR C
REPEAT B TIMES (
    INCREASE C
    INCREASE C
    INCREASE C
)

REPEAT C TIMES (

    # If X == 1 then skip body
    CLEAR D
    INCREASE D
    CLEAR E
    REPEAT X TIMES (
        REPEAT E TIMES ( CLEAR D )
        INCREASE E
    )

    CLEAR F
    INCREASE F
    REPEAT D TIMES ( CLEAR F )

    REPEAT F TIMES (

        # Unified pass for parity (G) and I = ceil(X/2)
        CLEAR G
        CLEAR I
        CLEAR J
        INCREASE J

        REPEAT X TIMES (
            CLEAR H
            REPEAT G TIMES ( INCREASE H )
            CLEAR G
            INCREASE G
            REPEAT H TIMES ( CLEAR G )

            REPEAT J TIMES ( INCREASE I )

            CLEAR H
            REPEAT J TIMES ( INCREASE H )
            CLEAR J
            INCREASE J
            REPEAT H TIMES ( CLEAR J )
        )

        # K = 3X + 1 computed only if odd
        CLEAR K
        INCREASE K
        REPEAT G TIMES (
            REPEAT X TIMES ( INCREASE K INCREASE K INCREASE K )
        )

        # Rebuild X from branches
        CLEAR X

        # even branch: X = I
        CLEAR L
        INCREASE L
        REPEAT G TIMES ( CLEAR L )
        REPEAT L TIMES ( REPEAT I TIMES ( INCREASE X ) )

        # odd branch: X = K
        REPEAT G TIMES ( REPEAT K TIMES ( INCREASE X ) )

        PRINT X
    )
)