### Database Schema:
CREATE TABLE country (
	id	INTEGER	NOT NULL	PRIMARY KEY,
	country_name	TEXT	NULL	DEFAULT NULL
);

CREATE TABLE ranking_criteria (
	id	INTEGER	NOT NULL	PRIMARY KEY,
	ranking_system_id	INTEGER	NULL	DEFAULT NULL,
	criteria_name	TEXT	NULL	DEFAULT NULL,
	foreign key (ranking_system_id) references ranking_system (id)
);

CREATE TABLE university (
	id	INTEGER	NOT NULL	PRIMARY KEY,
	country_id	INTEGER	NULL	DEFAULT NULL,
	university_name	TEXT	NULL	DEFAULT NULL,
	foreign key (country_id) references country (id)
);

CREATE TABLE university_ranking_year (
	university_id	INTEGER	NULL	DEFAULT NULL,
	ranking_criteria_id	INTEGER	NULL	DEFAULT NULL,
	year	INTEGER	NULL	DEFAULT NULL,
	score	INTEGER	NULL	DEFAULT NULL,
	foreign key (university_id) references university (id),
	foreign key (ranking_criteria_id) references ranking_criteria (id)
);

CREATE TABLE university_year (
	university_id	INTEGER	NULL	DEFAULT NULL,
	year	INTEGER	NULL	DEFAULT NULL,
	num_students	INTEGER	NULL	DEFAULT NULL,
	student_staff_ratio	REAL	NULL	DEFAULT NULL,
	pct_international_students	INTEGER	NULL	DEFAULT NULL,
	pct_female_students	INTEGER	NULL	DEFAULT NULL,
	foreign key (university_id) references university (id)
);

CREATE TABLE ranking_system (
	id	INTEGER	NOT NULL	PRIMARY KEY,
	system_name	TEXT	NULL	DEFAULT NULL
);

### User's Query:
What is the country ID of the University of Tokyo?

### Extra Knowledge:
University of Tokyo refers to university_name = 'University of Tokyo';
SELECT country_id FROM university WHERE university_name = 'University of Tokyo'