enter v 1
enter v 2
enter v 3
used to 1
2 0

enter v 4
used to 2
3 1

enter v 5
enter v 6
enter v 7
enter v 8
used to 5
7 4

enter v 10
enter v 9
enter v 11
used to 10
10 8

v = 9
9 8

v = 10
8 8

used to 11
8 10

v = 8
4 8

8 10
v = 7
6 4

v = 6
5 4

v = 5
4 4

used to 8
4 7

v = 4
1 4

4 5
v = 3
0 1

v = 2
1 0

used to 4
0 3

v = 1
0 0

used to 3
0 2