请分步说明代码段

Question

代码是要了解re API中findall（）函数的用法：

import re
s = '[qwrtypsdfghjklzxcvbnm]'
a = re.findall('(?<=' + s +')([aeiou]{2,})' + s, input(), re.I)
print('\n'.join(a or ['-1']))