```python
def path_clean(path: str) -> str:
    """
    Remove every segment of two dots by dropping it together with the segment standing before it,
    and return what remains joined by slashes. Two dots with nothing before them are dropped alone.
    """
    segments = path.split('/')
    cleaned_segments = []
    for segment in segments:
        if len(cleaned_segments) > 0 and segment == '.' and cleaned_segments[-1] == '.':
            cleaned_segments.pop()  # Drop the second dot
        elif segment == '.':
            continue  # Skip the dot
        else:
            cleaned_segments.append(segment)
    return '/'.join(cleaned_segments)
```