Function: gradient[0](sum(numbers("per") if minus(numbers("per") if numbers('yxy') > numbers("yyy") else numbers('yyx'), numbers("per")) > numbers("yyy") if numbers("per") > numbers('yxy') else numbers('yyx') else numbers("yyy"), minus(numbers('yyx') if numbers("yyy") > numbers('yxy') else numbers("per"), numbers("per"))))
