Write a function to find the closest smaller number than n.
def closest_num(N):
  return (N - 1)
<s>[INST]<<SYS>>Given a task and its code, generate test cases for the code.<</SYS>>Write a function to find the closest smaller number than n.
def closest_num(N):
  return (N - 1)[/INST]assert closest_num(11) == 10
assert closest_num(7) == 6
assert closest_num(12) == 11</s>