Give the cohort name for the school with biggest cohort size.
biggest cohort size refers to MAX(cohort_size); cohort = '4y bach' means bachelor's or equivalent-seeking cohort at 4-year institutions; cohort = '4y other' means students seeking another type of degree or certificate at a 4-year institution; cohort = '2y all' means degree-seeking students at 2-year institutions;
SELECT DISTINCT T1.chronname FROM institution_details AS T1 INNER JOIN institution_grads AS T2 ON T2.unitid = T1.unitid WHERE T1.cohort_size = ( SELECT MAX(T1.cohort_size) FROM institution_details AS T1 INNER JOIN institution_grads AS T2 ON T2.unitid = T1.unitid )