Build error android with 2 ad networks

When adding a second ad network into the project and trying to build, I get an error. Does anyone know how to fix it? This is the error:

 Error building Player: CommandInvokationFailure: Unable to convert classes into dex format. See the Console for details.
 C:\Program Files\Java\jdk1.8.0_40\bin\java.exe -Xmx2048M -Dcom.android.sdkmanager.toolsdir="C:/Program Files (x86)/Android SDK/adt-bundle-windows-x86_64-20140702/sdk\tools" -Dfile.encoding=UTF8 -jar "C:/Users/Shay/Documents/Unity/Editor/Data/BuildTargetTools/AndroidPlayer\sdktools.jar" -
 
 stderr[
 
 UNEXPECTED TOP-LEVEL EXCEPTION:
 java.lang.IllegalArgumentException: already added: Lcom/google/android/gms/internal/qn;
     at com.android.dx.dex.file.ClassDefsSection.add(ClassDefsSection.java:122)
     at com.android.dx.dex.file.DexFile.add(DexFile.java:161)
     at com.android.dx.command.dexer.Main.processClass(Main.java:732)
     at com.android.dx.command.dexer.Main.processFileBytes(Main.java:673)
     at com.android.dx.command.dexer.Main.access$300(Main.java:83)
     at com.android.dx.command.dexer.Main$1.processFileBytes(Main.java:602)
     at com.android.dx.cf.direct.ClassPathOpener.processArchive(ClassPathOpener.java:284)
     at com.android.dx.cf.direct.ClassPathOpener.processOne(ClassPathOpener.java:166)
     at com.android.dx.cf.direct.ClassPathOpener.processDirectory(ClassPathOpener.java:229)
     at com.android.dx.cf.direct.ClassPathOpener.processOne(ClassPathOpener.java:158)
     at com.android.dx.cf.direct.ClassPathOpener.process(ClassPathOpener.java:144)
     at com.android.dx.command.dexer.Main.processOne(Main.java:632)
     at com.android.dx.command.dexer.Main.processAllFiles(Main.java:510)
     at com.android.dx.command.dexer.Main.runMonoDex(Main.java:280)
     at com.android.dx.command.dexer.Main.run(Main.java:246)
     at com.android.dx.command.dexer.Main.main(Main.java:215)
     at com.android.dx.command.Main.main(Main.java:106)
     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
     at java.lang.reflect.Method.invoke(Method.java:497)
     at SDKMain.main(SDKMain.java:130)
 1 error; aborting
 ]