def merge(intervals: List[List[int]]) -> List[List[int]]:
    intervals.sort()
    merged_intervals = [intervals[0]]
    for interval in intervals:
        if interval[0] <= merged_intervals[-1][1]:
            merged_intervals[-1] = [merged_intervals[-1][0], max(merged_intervals[-1][1], interval[1])]
        else:
            merged_intervals.append(interval)
    return merged_intervals