def add(x, lst = []):
    if x not in lst:
        lst.append(x)
        
    return lst

def main():
    list1 = add(1)
    print(list1)

    list2 = add(2)
    print(list2)

    list3 = add(3, [11, 12, 13, 14])
    print(list3)

    list4 = add(4)
    print(list4)

main()