Error While Installing the tools Via RubyGems (Gem::FilePermissionError) On Windows Operating System

I am trying to install the ruby based tool in my windows 10 operating system, while installing the package via RubyGems I am getting this error :

C:\windows\system32>gem install brakeman
ERROR:  While executing gem ... (Gem::FilePermissionError)
    You don't have write permissions for the C:/Ruby31-x64/bin directory.

Error Image

I am running this command as administrator, However still i am getting this error continusoly, Please advise me what to do