What is the Took Office Date of the Presidency that Left Office Incumbent?
CREATE TABLE table_55849 (
    "Presidency" real,
    "President" text,
    "Date of Birth" text,
    "Took office" real,
    "Left office" text
)
SELECT SUM("Took office") FROM table_55849 WHERE "Left office" = 'incumbent'
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: What is the Took Office Date of the Presidency that Left Office Incumbent? ### Input: CREATE TABLE table_55849 (
    "Presidency" real,
    "President" text,
    "Date of Birth" text,
    "Took office" real,
    "Left office" text
) ### Response: SELECT SUM("Took office") FROM table_55849 WHERE "Left office" = 'incumbent'