ptfl (PtNode n@(x, lv) lt rt) acc tgt =
    if x == tgt
        then Just n
        else
            if x < tgt
                then acc
                else ptfl rt (jnl acc n) tgt
ptfl (PtNode n@(x, lv) lt rt) acc tgt =
    if x == tgt
        then Just n
        else
            if x < tgt
                then acc
                else ptfl rt (jnl acc n) tgt
ptfl (PtNode n@(x, lv) lt rt) acc tgt =
    if x == tgt
        then Just n
        else
            if x < tgt
                then acc
                else ptfl rt (jnl acc n) tgt