2
a_1
a_2
b_1
b_2
3
3	b_1
3	b_2
3	a_1
3	a_2
a_1	b_1
a_2	b_2
3
3
3
3
3
3
3
3
a_1	3
a_2	3
b_1	3
b_2	3
a_1	b_1	3
a_2	b_2	3