# Learn Recursion by Solving the Tower of Hanoi Puzzle - Step 24

### Tell us what’s happening:

The other case in which you have to move the disk necessarily from `source` to `target` is when the source list is not empty and the last disk in `source` is lower than the last disk in `target`.

Add an `elif` statement to check this condition. Then, set the `forward` variable to `True` if the condition is met.

I keep getting an error on this one too!

``````NUMBER_OF_DISKS = 3
number_of_moves = 2**NUMBER_OF_DISKS - 1
rods = {
'A': list(range(NUMBER_OF_DISKS, 0, -1)),
'B': [],
'C': []
}

def move(n, source, auxiliary, target):
# display starting configuration
print(rods)
for i in range(number_of_moves):
remainder = (i + 1) % 3
if remainder == 1:
print(f'Move {i + 1} allowed between {source} and {target}')
forward = False

# User Editable Region

if not rods[target]:
forward = True
elif rods[source] not [] and rods[source][-1] < rods[target][-1]:
forward = True

# User Editable Region

elif remainder == 2:
print(f'Move {i + 1} allowed between {source} and {auxiliary}')
elif remainder == 0:
print(f'Move {i + 1} allowed between {auxiliary} and {target}')

# initiate call from source A to target C with auxiliary B
move(NUMBER_OF_DISKS, 'A', 'B', 'C')
``````

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### Challenge Information:

Learn Recursion by Solving the Tower of Hanoi Puzzle - Step 24

This is not valid syntax. You cannot use `not` like that. Here you need to check that `rods[source]` is not empty, which means that `rods[source]` should return `True` when evaluated as a condition. You don’t need to use `not` or compare it with anything else.

``````elif rods[source] not [] and rods[source][-1] < rods[target][-1]:
forward = True
``````

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``````removed
``````

write this piece of code…