Function: gradient[0](sum(minus(minus(numbers('rep'), numbers('epe')) if product(minus(numbers('rep'), numbers('epe')), numbers('rep')) > numbers('rep') else numbers('epe'), product(minus(numbers('rep'), numbers('epe')), numbers('rep'))), product(minus(numbers('rep'), numbers('epe')), numbers('rep')) if numbers('epe') > minus(numbers('rep'), numbers('epe')) else numbers('rep')))
