AndroidStudio Include SDK in external C++ library

Hello, I’m a absolute beginner in Android Studio.
I’m need to do a external C++ library in Android Studio with just the function exchange(string FileIn, string FileOut).

I use the sample project in the SDK. I have created a module with a simple function. All is OK with my unity project. But now I want include the SDK in this module but AndroidStudio say he doesn’t found it .
What must I do to include the SDK in my module ?

#include <jni.h>
#include <A3DSDKIncludes.h>

extern “C”{
int getSomeNumber()
return 134;

int Add (int i, int j)
    return i+j;