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You are given a paragraph, with numbered sentences, and a question. Write the numbers of the sentences needed to answer the given question. Separate multiple sentence numbers with a comma (", "). E.g. "1, 2" would be the correct response if Sent 1 and Sent 2 are needed to answer the given question (do not include sentences that contain no information that is necessary to answer the question). Sort the sentence numbers in an increasing order (i.e., '1, 2', instead of '2, 1'). Your answer should not contain anything than the sentence numbers separated by a comma (e.g. '1, 2, 3, 4'). The given question requires more than one sentence to answer. So, your answer must contain at least one comma (", ").

Paragraph- Sent 1: (CNN) -- English club Chelsea have completed the signing of Oriol Romeu from Spanish and European champions Barcelona.
Sent 2: The 19-year-old is currently playing for Spain at the World Under-20 Championships in Colombia and has signed a four-year deal with last season's Premier League runners-up.
Sent 3: The deal is worth $7 million and includes a buy back clause, set at $14 million after the first year and $21 million after the second.
Sent 4: Romeu started his career at Barcelona's city rivals Espanyol before joining the Camp Nou academy in 2004.
Sent 5: The midfielder, who can also play in central defence, made his debut for Barcelona in last season's Spanish Supercup match with Seville and got his first taste of league action against Deportivo in May 2010.
Sent 6: He has played 90 minutes in both of Spain's games at the World Under-20 Championships, when they beat Costa Rica and Ecuador.
Sent 7: Chelsea official web site confirmed the signing and said Romeu is "renowned for his strength and his expansive passing ability."Sent 8: Another player leaving Barcelona is Jeffren Suarez after he agreed to join Sporting Lisbon.
Sent 9: The Portuguese outfit have paid $5 million for the 23-year-old which, like the Romeu deal, includes a buy back option.
Sent 10: Jeffren joined Barca from Tenerife in 2004 and made his debut for the Catalan club in the 2006-07 season. 
Question: What position did Romeu play when he started his career at Barcelona's city rivals Espanyol?.
Output:
4, 5.