-keepattributes *Annotation*
-keepclassmembers class com.google.**.R$* {
    public static <fields>;
}
-keep public class com.google.ads.** {*;}
-keep public class com.google.android.gms.** {*;}
-keep public class com.tappx.** { *; }
-keep public class com.android.installreferrer.** { *; }