Tell the number of papers that were presented at "International Symposium on Software Testing and Analysis" conference.
'International Symposium on Software Testing and Analysis' is the FullName of the conference; papers refers to Paper.Id
SELECT COUNT(T1.Id) FROM Paper AS T1 INNER JOIN Conference AS T2 ON T1.ConferenceId = T2.Id WHERE T2.FullName = 'International Symposium on Software Testing and Analysis'