<Tr> <Td> 1 . </Td> <Td> "Season of Glass" (Intro) </Td> <Td> </Td> <Td> <Ul> <Li> Iggy </Li> <Li> Seo Yong - bae </Li> </Ul> </Td> <Td> <Ul> <Li> Iggy </Li> <Li> Seo </Li> </Ul> </Td> <Td> 1: 13 </Td> </Tr> <Ul> <Li> Iggy </Li> <Li> Seo Yong - bae </Li> </Ul> <Li> Seo Yong - bae </Li> <Ul> <Li> Iggy </Li> <Li> Seo </Li> </Ul>

How many years did gfriend practice glass bead