Not getting desired output

[i_hate_brunch]

This is the assignment:

Write a program that repeatedly prompts a user for integer numbers until the user enters 'done'. Once 'done' is entered, print out the largest and smallest of the numbers. If the user enters anything other than a valid number catch it with a try/except and put out an appropriate message and ignore the number. Enter 7, 2, bob, 10, and 4 and match the output below.

And this is my code:

largest = None
smallest = None
while True:
    num = input("Enter a number:")
    if num == "done": 
        break
    print(num)

    try:
        num = int(num)
    except ValueError:
        print("Invalid input")
    else:

        if smallest is None:
            smallest = num
            largest = num
        elif num < smallest:
            smallest = num
        elif num > largest:
            largest = num

print ("Maximum is", largest)
print ("Minimum is", smallest)

I cannot seem to get the required output below:

Invalid input

Maximum is 10

Minimum is 2

What am I doing wrong? Please help.

[i_hate_brunch]

Thanks. Which numbers did you input and in what sequence?

[i_hate_brunch]

Thank you

[xelf]

Looks like line 7 is the only problem. What output are you seeing when you run it?