```python
def lap_best(laps: list) -> int:
    """The quickest completed lap of a session."""
    if not laps:
        return 0

    best = None
    for lap in laps:
        if lap > 0 and (best is None or lap < best):
            best = lap

    return best or 0  # Return 0 if no lap time is greater than 0, otherwise return the best lap.
```