user: You are a structured reasoning expert tasked with solving problems step by step. 
You first think about the reasoning process in the mind and then provide the answer. The reasoning process and answer should be enclosed within <think> </think> and <answer> </answer> tags, respectively, i.e., <think> reasoning process here </think> <answer> answer here </answer>. 
Given a question and the associated knowledge graph triplets (entity, relation, entity), you are asked to answer the question with these triplets and your own knowledge. 
You can break down the original question into several sub-questions and explore the given knowledge graph to solve them step-by-step. If there are multiple possible answers, choose one as the final answer. 
After thinking, when you finally reach a conclusion, clearly state the answer within <answer> </answer> tags, i.e., <answer> answer here </answer>. 
Question: Which WWII era US president was once White House Chief of Staff? 
Knowledge Triplets: 1940s, common.topic.webpage, m.09y8qhr
President of the United States, government.government_office_or_title.jurisdiction, United States of America
Executive Office of the President of the United States, business.employer.employees, m.04fvqsf
White House Chief of Staff, common.topic.notable_for, g.1258244g0
Executive Office of the President of the United States, common.topic.webpage, m.05t5j16
World War II, common.topic.webpage, m.09xrmvz
White House Chief of Staff, fictional_universe.character_occupation.characters_with_this_occupation, David Patrick
World War II, book.periodical_subject.periodicals, The War Illustrated
World War II, common.topic.image, m.02923_6
m.09xwgl8, common.webpage.topic, World War II
m.09xss79, common.webpage.topic, World War II
m.05bp25j, government.government_position_held.office_position_or_title, White House Chief of Staff
World War II, common.topic.subject_of, May 10-1940 Germany Invades Holland!
White House Chief of Staff, government.government_office_or_title.office_holders, m.05bp2ml
White House Ghosts: Presidents and Their Speechwriters, book.written_work.subjects, President of the United States
World War I, base.culturalevent.event.entity_involved, Woodrow Wilson
World War II, base.morelaw.war.peace_treaty, Treaty of Peace with Italy, 1947
World War II, common.topic.webpage, m.0b48g2t
m.09y9l5w, common.webpage.topic, World War II
m.09wsxxn, common.webpage.topic, World War II
m.0b48dsf, common.webpage.topic, World War II
m.09yjnz5, common.webpage.topic, World War II
Dwight D. Eisenhower, common.topic.notable_types, US President
World War II, time.event.locations, Africa
World War II, base.morelaw.war.peace_treaty, Paris Peace Treaties, 1947
World War II, common.topic.webpage, m.09x_3c3
Executive Office of the President of the United States, business.employer.employees, m.04g5nkk
World War II, common.topic.webpage, m.0b46rff
1940s, common.topic.image, World War II montage image
White House Chief of Staff, government.government_office_or_title.office_holders, m.05bp25j
World War II, common.topic.webpage, m.09wwp1v
World War II, base.morelaw.war.peace_treaty, Tripartite Pact
Ronald Reagan, military.military_person.participated_in_conflicts, World War II
m.048zk8w, government.government_position_held.office_position_or_title, White House Chief of Staff
1940s, common.topic.webpage, m.09y8qv3
Executive Office of the President of the United States, business.employer.employees, m.05f1814
World War II, common.topic.webpage, m.09y8d_t
Cold War, time.event.included_in_event, 1940s
World War II, base.morelaw.war.peace_treaty, Atlantic Charter
US President, common.topic.article, m.03yy9v6
m.05bp2ml, government.government_position_held.office_position_or_title, White House Chief of Staff
Executive Office of the President of the United States, business.employer.employees, m.07lqq51
Executive Office of the President of the United States, business.employer.employees, m.05ptxwr
m.05bp251, government.government_position_held.office_position_or_title, White House Chief of Staff
Executive Office of the President of the United States, business.employer.employees, m.05fvf05
White House Chief of Staff, government.government_office_or_title.office_holders, m.05bp2gf
m.05bp2p6, government.government_position_held.office_position_or_title, White House Chief of Staff
1940s, common.topic.image, 1944 NormandyLST
Executive Office of the President of the United States, business.employer.employees, m.0jsfrks
1940s, common.topic.notable_types, Event
World War II, common.topic.webpage, m.09y0608
World War II, common.topic.webpage, m.09y2gbs
m.010r2vx8, government.government_position_held.basic_title, White House Chief of Staff
Executive Office of the President of the United States, business.employer.employees, m.04j978b
m.05bp2fc, government.government_position_held.office_position_or_title, White House Chief of Staff
m.02h7np1, military.military_command.military_conflict, World War II
1940s, common.topic.webpage, m.09wxttg
World War II, common.topic.webpage, m.09y4ljx
m.0b46p4g, common.webpage.topic, World War II
White House Chief of Staff, government.government_office_or_title.office_holders, m.05bp2dq
m.02923_6, common.image.appears_in_topic_gallery, World War II
United States of America, people.person.nationality, Harry S. Truman
White House Chief of Staff, common.topic.webpage, m.09xhyz5
m.05bp2nn, government.government_position_held.office_position_or_title, White House Chief of Staff
m.0478pm4, military.military_command.military_conflict, World War II
m.05b8tvx, government.government_position_held.office_position_or_title, White House Chief of Staff
White House Chief of Staff, government.government_office_or_title.office_holders, m.05bp2ny
1940s, common.topic.webpage, m.09y8qss
1940s, time.event.includes_event, Cold War
David Patrick, fictional_universe.fictional_character.occupation, White House Chief of Staff
m.02h7nn7, military.military_command.military_conflict, World War II
Harry S. Truman, military.military_person.participated_in_conflicts, World War I
m.09x7jp_, common.webpage.topic, World War II
m.09y8d_t, common.webpage.topic, World War II
Dwight D. Eisenhower, military.military_person.participated_in_conflicts, World War I
World War II, common.topic.webpage, m.09wgp7j
World War II, common.topic.article, m.081q5
Executive Office of the President of the United States, business.employer.employees, m.04fvqjr
Executive Office of the President of the United States, business.employer.employees, m.0g9bfz1
US President, freebase.type_profile.published, Published
World War II, base.jewlib.jewish_studies_field.collections, Holocaust Era Assets
World War II, base.morelaw.war.peace_treaty, Pact of Steel
World War II, base.skosbase.vocabulary_equivalent_topic.narrower_concept, World War, 1939-1945--Hostages
1940s, common.topic.webpage, m.09y8qz2
World War II, common.topic.webpage, m.09ydx3t
m.05bp2f0, government.government_position_held.office_position_or_title, White House Chief of Staff
m.05bp2qn, government.government_position_held.office_position_or_title, White House Chief of Staff
World War II, common.topic.webpage, m.09w9d_p
m.05bh_20, government.government_position_held.office_position_or_title, White House Chief of Staff
Executive Office of the President of the United States, business.employer.employees, m.05fztvn
1940s, time.event.includes_event, World War II
m.0j34rt6, government.government_position_held.office_position_or_title, White House Chief of Staff
m.09w7qyh, common.webpage.topic, World War II
World War II, common.topic.webpage, m.0b49czw
World War II, common.topic.webpage, m.0b48dsf
White House Chief of Staff, government.government_office_or_title.office_holders, m.05bh_20
m.09xyz9p, common.webpage.topic, World War II
John F. Kennedy, military.military_person.participated_in_conflicts, World War II
World War II, common.topic.webpage, m.0b45zcq
m.09xxnlt, common.webpage.topic, World War II
World War II, common.topic.webpage, m.09yjnz5
George H. W. Bush, military.military_person.participated_in_conflicts, World War II
George Washington, first President of the United States, common.image.size, m.02f0j1t
World War II, common.topic.webpage, m.09wl5j0
World War II, military.military_conflict.commanders, m.02h7nns
World War II, time.event.locations, Middle East
World War II, common.topic.webpage, m.0b6rtrx
World War II, common.topic.webpage, m.0b46p4g
m.05nn8kj, common.webpage.topic, White House Chief of Staff
World War II, common.topic.image, WW2Montage
m.0b45zcq, common.webpage.topic, World War II
White House Chief of Staff, fictional_universe.character_occupation.characters_with_this_occupation, Vanessa Keller
World War II, base.morelaw.war.peace_treaty, Treaty of Vis
m.09wxv0j, common.webpage.topic, World War II
Donald Regan, military.military_person.participated_in_conflicts, World War II
World War II, common.topic.webpage, m.09x5b2d
World War II, common.topic.webpage, m.09xq5z0
m.09wwvtm, common.webpage.topic, World War II
World War II, common.topic.notable_for, g.125500wpl
World War II, base.morelaw.war.peace_treaty, Anglo-Soviet Agreement
1940s, common.topic.webpage, m.09y8qrg
m.0cqm322, common.webpage.topic, World War II
World War II, common.topic.webpage, m.09y5hqr
m.09ydx3t, common.webpage.topic, World War II
m.0b49czw, common.webpage.topic, World War II
White House Chief of Staff, government.government_office_or_title.office_holders, m.05bp2dc
World War II, common.topic.webpage, m.09w7nt9
White House Chief of Staff, government.government_office_or_title.office_holders, m.05bp2qn
1940s, common.topic.webpage, m.09x0ygq
m.09yybjl, common.webpage.topic, World War II
m.09wgp4k, common.webpage.topic, World War II
Executive Office of the President of the United States, business.employer.employees, m.05kf97n
m.09y6kxc, common.webpage.topic, World War II
m.09ygg0r, common.webpage.topic, World War II
Executive Office of the President of the United States, business.employer.employees, m.07lqw_r
World War II, common.topic.webpage, m.09xr1l4
m.05bp2dc, government.government_position_held.office_position_or_title, White House Chief of Staff
20th century, time.event.includes_event, World War II
World War II, common.topic.webpage, m.09yggz2
m.02h7nns, military.military_command.military_conflict, World War II
m.09xgynp, common.webpage.topic, World War II
World War II, common.topic.webpage, m.09wwvtm
White House Chief of Staff, government.government_office_or_title.governmental_body_if_any, Executive Office of the President of the United States
m.05bp2dq, government.government_position_held.office_position_or_title, White House Chief of Staff
1940s, common.topic.webpage, m.09y9lhh
White House Chief of Staff, common.topic.article, m.01f632
World War II, time.event.locations, Atlantic Ocean
1940s, time.event.included_in_event, 20th century
m.09xhyz5, common.webpage.topic, White House Chief of Staff
Executive Office of the President of the United States, business.employer.employees, m.05t2f6g
World War II, common.topic.webpage, m.09yybjl
White House Chief of Staff, government.government_position_held.office_position_or_title, m.05bp2h2
Holocaust Era Assets, base.jewlib.research_collection.jewish_studies_fields, World War II
President of the United States, book.book_subject.works, White House Ghosts: Presidents and Their Speechwriters
United States of America, military.military_combatant.belongs_to_combatant_group, Allies of World War II
World War II, time.event.locations, Southeast Asia
Executive Office of the President of the United States, business.employer.employees, m.0gll2xk
m.09y4ljx, common.webpage.topic, World War II
President of the United States, government.government_office_or_title.office_holders, m.03fx817
m.04jx14r, military.military_command.military_commander, Harry S. Truman
White House Chief of Staff, government.government_office_or_title.office_holders, m.05bp2n1
m.02h77t6, military.military_command.military_conflict, World War II
m.09yvl19, common.webpage.topic, World War II
Executive Office of the President of the United States, business.employer.employees, m.0jsfrll
1940s, common.topic.webpage, m.0b477mz
Executive Office of the President of the United States, business.employer.employees, m.05tsb1p
Rahm Emanuel, base.obamabase.cabinet_member.cabinet_position, White House Chief of Staff
World War II, common.topic.webpage, m.09xgynp
m.04jx14r, military.military_command.military_conflict, World War II
George S. Patton, military.military_person.participated_in_conflicts, World War II
m.05bp2g3, government.government_position_held.office_position_or_title, White House Chief of Staff
World War II, base.morelaw.war.peace_treaty, Sino-American Cooperative Organization
World War II, common.topic.webpage, m.09wxv0j
m.09wsrnl, common.webpage.topic, World War II
White House Chief of Staff, government.government_office_or_title.office_holders, m.01z0qwq
m.09ys_2c, common.webpage.topic, World War II
m.09wgp7j, common.webpage.topic, World War II
World War II, common.topic.image, World War II montage image
Executive Office of the President of the United States, business.employer.employees, m.05g5t96
President of the United States, book.book_subject.works, Presidential Leadership: Rating the Best and the Worst in the White House
White House Ghosts: Presidents and Their Speechwriters, common.topic.notable_for, g.1256y2f91
White House Chief of Staff, government.government_office_or_title.office_holders, m.05bp2f0
World War II, common.topic.webpage, m.09x773p
World War II, event.speech_or_presentation.speech_topic, m.05rpn5h
World War, 1939-1945--Hostages, base.skosbase.skos_concept.broader_topic, World War II
World War II, common.topic.webpage, m.09y6kxc
World War II, time.event.included_in_event, 20th century
Executive Office of the President of the United States, business.employer.employees, m.07f84gp
m.09x5b2d, common.webpage.topic, World War II
World War II, common.topic.webpage, m.09ys_2c
World War II, base.morelaw.war.peace_treaty, Franco-Soviet Treaty of Mutual Assistance
m.09y5hqr, common.webpage.topic, World War II
George Washington, first President of the United States, common.image.appears_in_topic_gallery, Charles Lee
1940s, common.topic.article, m.08b8s
1940s, common.topic.webpage, m.09x0bz7
World War II, common.topic.webpage, m.09wsrnl
m.050_mr9, fictional_universe.fictional_employment_tenure.title, White House Chief of Staff
World War II, common.topic.webpage, m.0b49cc7
m.05bp2n1, government.government_position_held.office_position_or_title, White House Chief of Staff
m.09ybsfr, common.webpage.topic, World War II
1940s, common.topic.webpage, m.09x2qxc
Executive Office of the President of the United States, business.employer.employees, m.04j9779
White House Chief of Staff, common.topic.image, Whlogo1
White House Chief of Staff, common.topic.notable_types, Government Office or Title
m.09w9d_p, common.webpage.topic, World War II
m.05bp2fs, government.government_position_held.office_position_or_title, White House Chief of Staff
World War II, common.topic.webpage, m.09wsxxn
Richard Nixon, military.military_person.participated_in_conflicts, World War II
White House Chief of Staff, government.government_office_or_title.office_holders, m.05bp2g3
World War II, common.topic.webpage, m.09wgp4k
World War II, common.topic.webpage, m.09x7jp_
Dwight D. Eisenhower, government.us_president.vice_president, Richard Nixon
World War II, common.topic.webpage, m.09ysx61
m.02h7nnj, military.military_command.military_conflict, World War II
White House Chief of Staff, government.government_office_or_title.office_holders, m.04cnx_5
Dwight D. Eisenhower, military.military_person.participated_in_conflicts, World War II
World War II, common.topic.webpage, m.09xss79
White House Chief of Staff, government.government_office_or_title.office_holders, m.05bp2fs
US President, freebase.type_profile.kind, Title
m.05bp2gf, government.government_position_held.office_position_or_title, White House Chief of Staff
White House Chief of Staff, government.government_office_or_title.office_holders, m.0j34rt6
World War II, common.topic.webpage, m.09yf8lh
World War II, common.topic.webpage, m.09xwgl8
World War I, time.event.included_in_event, 20th century
World War II, common.topic.webpage, m.09ygg0r
White House Ghosts: Presidents and Their Speechwriters, common.topic.article, m.063qkhh
m.04cnx_5, government.government_position_held.office_position_or_title, White House Chief of Staff
President of the United States, common.topic.image, George Washington, first President of the United States
m.05bp2h2, government.political_appointer.appointees, Harry S. Truman
White House Chief of Staff, government.government_office_or_title.office_holders, m.048zk8w
Gerald Ford, military.military_person.participated_in_conflicts, World War II
White House Chief of Staff, government.government_office_or_title.office_holders, m.05bp2h2
Vanessa Keller, fictional_universe.fictional_character.occupation, White House Chief of Staff
World War II, common.topic.webpage, m.09w41xr
m.09y0608, common.webpage.topic, World War II
m.0b49cc7, common.webpage.topic, World War II
World War II, radio.radio_subject.programs_with_this_subject, D-Day: 40 Years Later
White House Chief of Staff, government.government_office_or_title.office_holders, m.05bp25v
White House Chief of Staff, government.government_office_category.officeholders, m.010r2vx8
White House Chief of Staff, base.schemastaging.context_name.pronunciation, m.01314r39
m.09x_3c3, common.webpage.topic, World War II
m.0b6rtrx, common.webpage.topic, World War II
White House Chief of Staff, base.obamabase.cabinet_position.potential_cabinet_members, Rahm Emanuel
World War II, military.military_conflict.commanders, m.04jx14r
Whlogo1, common.image.appears_in_topic_gallery, White House Chief of Staff
White House Chief of Staff, government.government_office_or_title.office_holders, m.05bp2fc
m.09w41xr, common.webpage.topic, World War II
World War II, common.topic.webpage, m.0cqm322
Herbert Hoover, common.topic.notable_types, US President
Executive Office of the President of the United States, business.employer.employees, m.05t2fmy
World War II, common.topic.webpage, m.09yvl19
World War II, common.topic.subject_of, The Price of the Victory
Executive Office of the President of the United States, government.governmental_body.offices_positions, White House Chief of Staff
m.09xrmvz, common.webpage.topic, World War II
George Washington, first President of the United States, common.image.appears_in_topic_gallery, The Imperial Presidency
m.0j35vth, government.government_position_held.office_position_or_title, White House Chief of Staff
m.05rpn5h, event.speech_or_presentation.speaker_s, Harry S. Truman
White House Chief of Staff, government.government_office_or_title.office_holders, m.05bp251
Executive Office of the President of the United States, business.employer.employees, m.07lqdkr
George W. Bush, government.us_president.vice_president, Dick Cheney
m.05bp2ny, government.government_position_held.office_position_or_title, White House Chief of Staff
World War II, common.topic.webpage, m.09yj2jt
White House Chief of Staff, government.government_office_or_title.office_holders, m.05bp2qb
1940s, common.topic.webpage, m.09y8qdv
White House Chief of Staff, base.descriptive_names.names.descriptive_name, m.0_z7y64
World War II, military.military_conflict.commanders, m.0w5t9rt
Executive Office of the President of the United States, common.topic.notable_for, g.125byqg1p
World War II, military.military_conflict.commanders, m.02h7nn7
World War II, common.topic.webpage, m.09xyz9p
Lyndon B. Johnson, military.military_person.participated_in_conflicts, World War II
Executive Office of the President of the United States, business.employer.employees, m.04hym8x
World War II montage image, common.image.appears_in_topic_gallery, 1940s
President of the United States, book.book_subject.works, Presidential Command: Power, Leadership, and the Making of Foreign Policy from Richard Nixon to George W. Bush
m.09xq5z0, common.webpage.topic, World War II
m.09x4cx1, common.webpage.topic, World War II
Executive Office of the President of the United States, business.employer.employees, m.07tk_2z
m.01z0qwq, government.government_position_held.office_position_or_title, White House Chief of Staff
George Washington, first President of the United States, common.image.appears_in_topic_gallery, President of the United States
m.05bp2qb, government.government_position_held.office_position_or_title, White House Chief of Staff
White House Chief of Staff, fictional_universe.fictional_job_title.fictional_characters_with_this_job, m.050_mr9
World War, 1939-1945--Hostages, base.skosbase.skos_concept.in_scheme, Topical Terms Concept Scheme
Executive Office of the President of the United States, business.employer.employees, m.07lqk5d
World War II, time.event.locations, Europe
WW2Montage, common.image.appears_in_topic_gallery, World War II
George Washington, first President of the United States, common.image.appears_in_topic_gallery, Town Destroyer
World War II, common.topic.webpage, m.09ybsfr
m.09yggz2, common.webpage.topic, World War II
World War II, time.event.instance_of_recurring_event, World war
White House Chief of Staff, government.government_office_or_title.office_holders, m.05bp2gs
m.05bp2nc, government.government_position_held.office_position_or_title, White House Chief of Staff
m.09w7nt9, common.webpage.topic, World War II
1940s, common.topic.webpage, m.09y8q62
m.09wwp1v, common.webpage.topic, World War II
Executive Office of the President of the United States, business.employer.employees, m.04j9770
1940s, common.topic.webpage, m.09wt5nx
1940s, common.topic.webpage, m.0b4812t
Executive Office of the President of the United States, common.topic.image, محل استقرار ستاد
Franklin D. Roosevelt, government.us_president.vice_president, Harry S. Truman
White House Chief of Staff, base.schemastaging.context_name.plural, m.0w0qtks
Executive Office of the President of the United States, business.employer.employees, m.04j6cbg
World War II, common.topic.webpage, m.09y9l5w
White House Chief of Staff, government.government_office_or_title.office_holders, m.05bp2p6
1940s, common.topic.webpage, m.09y8qg4
m.09y2gbs, common.webpage.topic, World War II
White House Chief of Staff, government.government_office_or_title.office_holders, m.05b8tvx
World War II, time.event.locations, Asia
m.0b48g2t, common.webpage.topic, World War II
Executive Office of the President of the United States, business.employer.employees, m.07p2824
Executive Office of the President of the United States, business.employer.employees, m.0gll2z5
World War II, time.event.included_in_event, 1940s
White House Chief of Staff, government.government_office_or_title.office_holders, m.0j35vth
m.09yfzdj, common.webpage.topic, World War II
White House Chief of Staff, common.topic.webpage, m.05nn8kj
Executive Office of the President of the United States, business.employer.employees, m.0cgx45s
m.09yf8lh, common.webpage.topic, World War II
Ronald Reagan, government.us_president.vice_president, George H. W. Bush
President of the United States, freebase.type_profile.equivalent_topic, US President
George W. Bush, common.topic.notable_types, US President
World War II, common.topic.webpage, m.09x4cx1
Executive Office of the President of the United States, common.topic.image, Exec bldg
Executive Office of the President of the United States, business.employer.employees, m.04g5nft
m.03fx817, government.politician.government_positions_held, Harry S. Truman
m.0b475k_, common.webpage.topic, World War II
m.09wl5j0, common.webpage.topic, World War II
Allies of World War II, military.military_combatant.includes_allies, United States of America
George Washington, first President of the United States, common.image.appears_in_topic_gallery, Presidency of George Washington
Rahm Emanuel, base.obamabase.possible_cabinet_member.cabinet_position, White House Chief of Staff
Executive Office of the President of the United States, business.employer.employees, m.052m4fx
Executive Office of the President of the United States, business.employer.employees, m.04j6cc3
Executive Office of the President of the United States, business.employer.employees, m.04hdq2t
George Washington, first President of the United States, common.image.appears_in_topic_gallery, Powers of the President of the United States
m.09xr1l4, common.webpage.topic, World War II
Presidential Leadership: Rating the Best and the Worst in the White House, book.written_work.subjects, President of the United States
White House Chief of Staff, base.descriptive_names.names.descriptive_name, m.0_z7yc7
m.09ysx61, common.webpage.topic, World War II
White House Chief of Staff, government.government_office_or_title.office_holders, m.05bp2nn
Executive Office of the President of the United States, business.employer.employees, m.052lflh
m.05bp2h2, government.government_position_held.office_position_or_title, White House Chief of Staff
World War II, common.topic.webpage, m.09w7qyh
m.05bp25v, government.government_position_held.office_position_or_title, White House Chief of Staff
Executive Office of the President of the United States, business.employer.employees, m.052lsqd
m.05bp2gs, government.government_position_held.office_position_or_title, White House Chief of Staff
White House Chief of Staff, government.government_office_or_title.office_holders, m.05bp2nc
m.09yj2jt, common.webpage.topic, World War II
George Washington, first President of the United States, common.image.appears_in_topic_gallery, George Washington
White House Chief of Staff, base.descriptive_names.names.descriptive_name, m.0_z7ywt
D-Day: 40 Years Later, radio.radio_program.subjects, World War II
World War II, common.topic.webpage, m.09xxnlt
m.0b46rff, common.webpage.topic, World War II
World War II, base.morelaw.war.peace_treaty, Nuremberg Charter
White House Chief of Staff, base.descriptive_names.names.descriptive_name, m.0_z7y6p
US President, common.topic.notable_types, Harry S. Truman
World War II, common.topic.webpage, m.0b475k_
m.09x773p, common.webpage.topic, World War II
World War II, common.topic.webpage, m.09yfzdj

Answer: Harry S. Truman