def merge_intervals(intervals: list[list[int]]) -> list[list[int]]:
    intervals.sort()
    result: list[list[int]] = intervals[:1]
    
    for start, end in intervals:
        if result and start <= (temp := result[-1][1]):
            result[-1][1] = max(temp, end)
        else:
            result += [start, end],

    return result