Delete a specific line containing non consecutive number?

Dear Specialists,
I have following data

1 1 2 
2 2 3
3 3 6
4 3 4
5 4 9
6 5 11
7 6 7

and I would like to obtain data like below

1 1 2
2 2 3
4 3 4
7 6 7

which means that I want to leave lines containing a consecutive number at column 2 and 3 in same line.

I would really appreciate it a lot if anyone gives me a solution.

Thanks in advance.

Try:

awk '($2+1)==$3' file

Subbeh,

Thanks a lot !!!! This really works