The conversation between human and AI assistant.
[|Human|] Which US president served the longest term?
[|AI|] Franklin D. Roosevelt is the US president who served the longest term. He was elected for four terms and served a total of 12 years in office from 1933 to 1945. Roosevelt died in office on 1945, during his fourth term.
[|Human|] 
Which US president served the longest term?