def merge_sort(arr):
    if len(arr) <= 1:
        return arr
    mid = len(arr) // 2
    left = arr[:mid]
    right = arr[mid:]
    merge_sort(left)
    merge_sort(right)
    return merge(left, right)

def merge(left, right):
    result = []
    i, j = 0, 0
    ———————————————————————————————
        if left[i] < right[j]:
            result.append(left[i])
            i += 1
        else:
            result.append(right[j])
            j += 1
    result += left[i:]
    result += right[j:]
    return result