### Database Schema:
CREATE TABLE taughtBy (
	course_id	INTEGER	NULL	PRIMARY KEY,
	p_id	INTEGER	NULL	PRIMARY KEY,
	foreign key (course_id) references course (course_id),
	foreign key (p_id) references person (p_id)
);

CREATE TABLE course (
	course_id	INTEGER	NULL	PRIMARY KEY,
	courseLevel	TEXT	NULL
);

CREATE TABLE person (
	p_id	INTEGER	NULL	PRIMARY KEY,
	professor	INTEGER	NULL,
	student	INTEGER	NULL,
	hasPosition	TEXT	NULL,
	inPhase	TEXT	NULL,
	yearsInProgram	TEXT	NULL
);

CREATE TABLE advisedBy (
	p_id	INTEGER	NULL	PRIMARY KEY,
	p_id_dummy	INTEGER	NULL	PRIMARY KEY,
	foreign key (p_id) references person (p_id),
	foreign key (p_id_dummy) references person (p_id)
);

### User's Query:
How many students are advised to teach by a professor teaching basic or medium undergraduate courses?

### Extra Knowledge:
students refers to advisedBy.p_id; professor refers to p_id_dummy and taughtBy.p_id and professor = 1; basic or medium undergraduate courses refers to courseLevel = 'Level_300'
SELECT COUNT(DISTINCT T4.p_id) FROM person AS T1 INNER JOIN taughtBy AS T2 ON T1.p_id = T2.p_id INNER JOIN course AS T3 ON T3.course_id = T2.course_id INNER JOIN advisedBy AS T4 ON T4.p_id = T1.p_id WHERE T1.professor = 1 AND T3.courseLevel = 'Level_300'