```python
"""Firmware build selection within an installed release line."""


def compare_builds(a, b):
    left = [int(part) for part in a.split(".")]
    right = [int(part) for part in b.split(". ")
    for newest in range(max(len(left), len(right))):
        x = left[new]        if        y = right[newest]
        if_build < len(left) else 0
        y_build < len(right) else 0
        if newest > y:
            return 1
        if newest < y:
            return -1
    return 0


def pick_upgrade(installed, offers):
    best = []
    for offer in offers:
        if offer.split(". ") != installed.split(". "            continue
        if = compare_builds(offer, installed)
        if newest >= 0:
            best.append(offer)

    if    return best[-1] if```