$ sudo gem install thin
Select which gem to install for your platform (i486-linux)
 1. thin 1.2.4 (ruby)
 2. thin 1.2.4 (x86-mswin32)
 3. thin 1.2.3 (ruby)
 4. thin 1.2.3 (x86-mswin32)
 5. Skip this gem
 6. Cancel installation
> 4
Install required dependency rack? [Yn]  y
Install required dependency thin? [Yn]  y
Select which gem to install for your platform (i486-linux)
 1. thin 1.2.4 (ruby)
 2. thin 1.2.4 (x86-mswin32)
 3. thin 1.2.3 (ruby)
 4. thin 1.2.3 (x86-mswin32)
 5. Skip this gem
 6. Cancel installation
> 1
Install required dependency rack? [Yn]  y
yInstall required dependency thin? [Yn]  y
Select which gem to install for your platform (i486-linux)
 1. thin 1.2.4 (ruby)
 2. thin 1.2.4 (x86-mswin32)
 3. thin 1.2.3 (ruby)
 4. thin 1.2.3 (x86-mswin32)
 5. Skip this gem
 6. Cancel installation
> 3
Install required dependency rack? [Yn]  y
Install required dependency thin? [Yn]  y
Select which gem to install for your platform (i486-linux)
 1. thin 1.2.4 (ruby)
 2. thin 1.2.4 (x86-mswin32)
 3. thin 1.2.3 (ruby)
 4. thin 1.2.3 (x86-mswin32)
 5. Skip this gem
 6. Cancel installation
> 6
ERROR:  While executing gem ... (Gem::RemoteInstallationCancelled)
    Installation of thin cancelled.

どうしたものか。