[질문] 쎈 수1(상) 137번답좀알려주세요

답은ㄱ.이네요..1,0,1,0,-1,0,1,0을반복합니다..그리고|An-1|은2,1,0,1,2,1,0,1을반복해서..값이0이될경우에는어떤k가오더라도상관없이|An-1|<k가됩니다..