A a
t1
1
B b
2
1
C c
2
1
D d
2
1
B b
2
12
1
D d
2
span
t3
1
span
2
1
span
2
1
span
2
12
1
span
2
12
1
span
2
12
1
span
2
span
1
span
2
1
span
2
1
span
2
span
1
span
2
1
span
2
1
span
2
span
1
span
2
1
span
2
1
span
2
span
1
span
2
1
span
2
1
span
2
1
span
2
1
span
2
1
span
2
1
span
2
1
span
2
1
span
2
1
span
2
1
span
2
1
span
2
span
1
span
2
1
span
2
1
span
2