Cannot resolve error in import com.facebook.ads

trying to add face book interstitial ads to my app, i am using this Facebook sdk in gradle.

implementation 'com.facebook.android:facebook-android-sdk:[5,6)'

and on calling import in my activity

import com.facebook.ads     

this gives error as ads package is not being resolved or does not exist.

How to add this import to work properly?

Cannot resolve error in import com.facebook.ads