For N = 9, I got the following result:

4*1738=6952

4*1963=7852

12*483=5796

18*297=5346

27*198=5346

28*157=4396

39*186=7254

42*138=5796

48*159=7632

sum = 56370

I passed all tests except the last one. Can someone please tell me what's going wrong here?