Question:
Which position did Denis McDonough hold in Sep, 2013?

Context:
 Denis McDonough holds the position of White House Chief of Staff from Jan, 2013 to Jan, 2017. 
 Denis McDonough holds the position of United States Secretary of Veterans Affairs from Feb, 2021 to Dec, 2022. 
 Denis McDonough holds the position of Deputy National Security Advisor from Oct, 2010 to Jan, 2013.

Answer:
White House Chief of Staff