List = input('''Please give me a list of random number here, like '2,35,5,32':
''')
num = input('''Please enter a number if you want to check what elements in your list is less than this number:
''')
List = List.split(',')
new_list = []
for i in List:
    if num == '':
        if int(i) < 5:
            new_list.append(i)
    else:
        if int(i) < int(num):
            new_list.append(i)
print (new_list)