Error building Player: CommandInvokationFailure: Failed to re-package resources.

Hi, I tried to show a banner in my game for Android with "Unity AdMob (Google Play Services) for Android". But, when I build the project, Unity shows me this error:

Error building Player: CommandInvokationFailure: Failed to re-package resources. See the Console for details. C:\Users\Ricardo\Desktop\Sistema\Miscelánea\Android SDK\adt-bundle-windows-x86_64-20140702\sdk\build-tools\21.0.1\aapt.exe package --auto-add-overlay -v -f -m -J gen -M AndroidManifest.xml -S "res" -I "C:/Users/Ricardo/Desktop/Sistema/Miscelánea/Android SDK/adt-bundle-windows-x86_64-20140702/sdk/platforms/android-21\android.jar" -F bin/resources.ap_ --extra-packages com.google.android.gms -S "C:\Users\Ricardo\Desktop\Sistema\Proyectos\Paper Race\Temp\StagingArea\android-libraries\google-play-services_lib\res"

I don't know what is the problem, so I would be very thankful if someone could help me.

Sorry for my bad english.