Formula Cannot Reference a Range on other sheets

Hi lovely people, I am trying to make the following forumula work: =LOOKUP(2,1/(((COUNTIF($A$1:A1, Input!$A$2:$A$200)=0)*(COUNTIF(Input!$A$2:$A$200, Input!$A$2:$A$200)>0.5))), Input!$A$2:$A$200...