user: Question: Who was first elected as the result of a Retired Republican gain in the district of Ohio 21?
Columns: ['District', 'Incumbent', 'Party', 'First elected', 'Result']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Ohio 1', 'Benjamin Butterworth', 'Republican', '1884', 'Re-elected']
SQL:

assistant: SELECT "First elected" FROM "Table" WHERE "Result" = 'Retired Republican gain' AND "District" = 'Ohio 21';