query on context change

Hi,

i am getting small problem in the context change..

i have input as

1

2

3

[3]context change

4

5

[5]conext change

6

7

8

[8]context change

i want out put as

2

3

[3]conext change

5

[5]context change

7

8

[8]context change

my requirement is the element after context change in the input sholud be deleted.

Thank you,

Madhav.