List the official full names of all the legislators that served 13 district for 26 consecutive years.
served only one district for 26 consecutive years refers to SUBTRACT(SUM(cast(strftime('%Y', end)), CAST(strftime('%Y', start)))) = 26
SELECT DISTINCT CASE WHEN SUM(CAST(strftime('%Y', T2.end) AS int) - CAST(strftime('%Y', T2.start) AS int)) = 26 THEN T1.official_full_name END FROM current AS T1 INNER JOIN `current-terms` AS T2 ON T1.bioguide_id = T2.bioguide GROUP BY T1.official_full_name, T2.district HAVING COUNT(T1.official_full_name) = 13