You see, as I type in the codes below, Python said that there was an ValueError. But what's below is literaly what I copied from the book, still didn't work. So I tried to type in this codes manully, but after I typed "a = int(input())" and press "Enter" to make a new statement, the prompt didn't show up. Next, I tried to type these in Notepad++, and saved as ".py", When I ran it, it said that there was an "invalid syntax". Is anything with the code? I'm about to lose my mind, please help me. 
a = int()
b = int()
a = int(input())
b = int(input())
print(a + b)
a = int()
b = int()
a = int(input())
b = int(input())
print(a + b)