unable to convert classes into dex format

I have looked at other questions from people with the same error but it seems like my error has a different cause, and the culprit seems to be unity ads. when I try to build for android, it fails and says "unable to convert classes into dex format, look at the console for more info". and in the console I have the following two errors:

CommandInvokationFailure: Unable to convert classes into dex format. See the Console for details. C:\Program Files\Java\jdk1.7.0_79\bin\java.exe -Xmx2048M -Dcom.android.sdkmanager.toolsdir="C:/Users/Ashkan/AppData/Local/Android/sdk\tools" -Dfile.encoding=UTF8 -jar "C:\Program Files\Unity 5.3.4\Editor\Data\PlaybackEngines\AndroidPlayer/Tools\sdktools.jar" -

stderr[ Exception in thread "main" java.lang.UnsupportedClassVersionError: com/android/dx/command/Main : Unsupported major.minor version 52.0 at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClass(ClassLoader.java:800) at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142) at java.net.URLClassLoader.defineClass(URLClassLoader.java:449) at java.net.URLClassLoader.access$100(URLClassLoader.java:71) at java.net.URLClassLoader$1.run(URLClassLoader.java:361) at java.net.URLClassLoader$1.run(URLClassLoader.java:355) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:354) at java.lang.ClassLoader.loadClass(ClassLoader.java:425) at java.lang.ClassLoader.loadClass(ClassLoader.java:358) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:274) at SDKMain.main(SDKMain.java:127) ] stdout[

] UnityEditor.Android.Command.Run (System.Diagnostics.ProcessStartInfo psi, UnityEditor.Android.WaitingForProcessToExit waitingForProcessToExit, System.String errorMsg) UnityEditor.Android.AndroidSDKTools.RunCommandInternal (System.String javaExe, System.String sdkToolsDir, System.String[] sdkToolCommand, Int32 memoryMB, System.String workingdir, UnityEditor.Android.WaitingForProcessToExit waitingForProcessToExit, System.String errorMsg) UnityEditor.Android.AndroidSDKTools.RunCommandSafe (System.String javaExe, System.String sdkToolsDir, System.String[] sdkToolCommand, Int32 memoryMB, System.String workingdir, UnityEditor.Android.WaitingForProcessToExit waitingForProcessToExit, System.String errorMsg) UnityEditor.HostView:OnGUI()

and the second error is :

Error building Player: CommandInvokationFailure: Unable to convert classes into dex format. See the Console for details. C:\Program Files\Java\jdk1.7.0_79\bin\java.exe -Xmx2048M -Dcom.android.sdkmanager.toolsdir="C:/Users/Ashkan/AppData/Local/Android/sdk\tools" -Dfile.encoding=UTF8 -jar "C:\Program Files\Unity 5.3.4\Editor\Data\PlaybackEngines\AndroidPlayer/Tools\sdktools.jar" -

stderr[ Exception in thread "main" java.lang.UnsupportedClassVersionError: com/android/dx/command/Main : Unsupported major.minor version 52.0 at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClass(ClassLoader.java:800) at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142) at java.net.URLClassLoader.defineClass(URLClassLoader.java:449) at java.net.URLClassLoader.access$100(URLClassLoader.java:71) at java.net.URLClassLoader$1.run(URLClassLoader.java:361) at java.net.URLClassLoader$1.run(URLClassLoader.java:355) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:354) at java.lang.ClassLoader.loadClass(ClassLoader.java:425) at java.lang.ClassLoader.loadClass(ClassLoader.java:358) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:274) at SDKMain.main(SDKMain.java:127) ] stdout[

]

even when I start a new project with only the unity Ads enabled, I still get the same error when I build for android. I don't have a problem with iOS. only android. I have looked into those directories that the error points to but I really don't know what I am looking at there or why those directories cause a problem. I have tried it with both unity 5.3.4 and 5.3.5 to no avail. any help would be greatly appreciated.