take the input and reassign the element in the index to x, then print the list

Question

items = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
num = int(input())
C=(items[num-1])
items[C]=("x")
print(items)
its working 3 out of 4 times, but the broken one is hidden, so i dont know what my error is. based on what its taught me, this should work

Answer 1

Maybe try C=num-1

Answer 2

I believe, the input value is the index to be used, but if it is a pro challenge, then non-pro users can't see the details of the challenge.
You just need to set the;
items[num] = 'x'
Then output items