Task: Question Answering
Input (English): Sentence: Although this period had been productive, the bad weather had such a detrimental effect on Chopin's health that Sand determined to leave the island. To avoid further customs duties, Sand sold the piano to a local French couple, the Canuts.[n 8] The group traveled first to Barcelona, then to Marseilles, where they stayed for a few months while Chopin convalesced. In May 1839 they headed for the summer to Sand's estate at Nohant, where they spent most summers until 1846. In autumn they returned to Paris, where Chopin's apartment at 5 rue Tronchet was close to Sand's rented accommodation at the rue Pigalle. He frequently visited Sand in the evenings, but both retained some independence. In 1842 he and Sand moved to the Square d'Orléans, living in adjacent buildings. 
Question: After returning to Paris where was Chopin's apartment?
Output (English): 5 rue Tronchet