Maybe locale issue...? Are you doing this by ssh or directly on device? On one of my servers due to locale mixup via ssh (server was utf-8, ssh connection was set up using eastern european windows locale) when I entered some characters it messed up the input (e.g. when apt was asking me something, it always translated to "no" on the server). Besides, when it aks you [Y/n] the bigger letter (in this case "Y") indicates that this is the default answer - have you tried just pressing "enter"? You could also force the "yes" answer by one of apt-get parameters, but I would not recommend it if you are not really experienced with apt, and this is rather a workaround then solution (and you should always first run the command without the "force yes" parameter, verify that result is what you expect, and then rerun the command with "force yes" parameter to actually run it without need for confirmation).