def merge(array1, array2):
    i = 0
    j = 0
    result = []
    while i < len(array1) and j < len(array2):
        if array1[i] <= array2[j]:
            result.append(array1[i])
            i += 1
        else:
            result.append(array2[j])
            j += 1
    return result + array1[i:] + array2[j:]

def merge_sort(array):
    if len(array) == 1:
        return array
    else:
        l = array[:len(array)//2]
        r = array[len(array)//2:]
        return merge(merge_sort(l), merge_sort(r))

print(merge_sort([9, 8, 1, 2]))