def merge_sort(array):

    if len(array) <= 1:

        return array

    middle = len(array) // 2

    left = merge_sort(array[:middle])

    right = merge_sort(array[middle:])

    return merge(left, right)

def merge(left, right):

    result = []

    i = 0

    j = 0

    while i < len(left) and j < len(right):

        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

if __name__ == "__main__":

    array = [12, 11, 13, 5, 6, 7, 1, 2, 3, 4]

    print(merge_sort(array))