How many papers are written by authors from the institution "University of Pennsylvania"?
SELECT count(DISTINCT t1.title) FROM papers AS t1 JOIN authorship AS t2 ON t1.paperid  =  t2.paperid JOIN inst AS t3 ON t2.instid  =  t3.instid WHERE t3.name  =  "University of Pennsylvania"
SELECT count(DISTINCT t1.title) FROM papers AS t1 JOIN authorship AS t2 ON t1.paperid  =  t2.paperid JOIN inst AS t3 ON t2.instid  =  t3.instid WHERE t3.name  =  "University of Pennsylvania"
[{'count(DISTINCT t1.title)': 1}]