will only show every 3rd line

Hi, how will i show every 3rd line of the file.
Ex.

line 1

line 2
line 3
line 4
line 5


line 6
line 7

Output:

line 2
line 5
line 6

tyhanks

---------- Post updated at 03:39 AM ---------- Previous update was at 03:37 AM ----------

vmstat
procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy id wa
 3  0    248 3500056 444596 11659336    0    0     6    47    0     2  4  3 93  0
 
sar 
Linux 2.6.9-67.ELsmp (eira4_dr) 	08/03/10

00:00:01          CPU     %user     %nice   %system   %iowait     %idle
00:00:02          all     11.75      0.00      7.25      0.00     81.00
00:00:03          all      0.75      0.00      0.25      0.00     99.00
00:00:04          all      0.00      0.00      0.00      0.00    100.00
00:00:05          all      0.25      0.00      0.25      0.00     99.50
00:00:06          all      0.00      0.00      0.00      0.25     99.75
Average:          all      2.55      0.00      1.55      0.05     95.85
Tue Aug  3 00:05:01 PHT 2010
 
vmstat
procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy id wa
 1  0    248 3499032 444596 11659404    0    0     6    47    0     2  4  3 93  0
 
sar 
Linux 2.6.9-67.ELsmp (eira4_dr) 	08/03/10

00:05:01          CPU     %user     %nice   %system   %iowait     %idle
00:05:02          all      7.71      0.00      1.00      0.25     91.04
00:05:03          all      0.00      0.00      0.00      0.00    100.00
00:05:04          all      0.50      0.00      0.50      0.00     99.00
00:05:05          all      0.25      0.00      0.50      0.00     99.25
00:05:06          all      5.01      0.00      2.01      0.00     92.98
Average:          all      2.70      0.00      0.80      0.05     96.45
Tue Aug  3 00:10:01 PHT 2010

---------- Post updated at 03:40 AM ---------- Previous update was at 03:39 AM ----------

[/COLOR]on my sample file i just want to get the data under vmstat under free with bold.

Something like this?

awk '/procs --/{getline;getline;print $4}'  file

dude you are genius... anyway you can use that for monitoring your free memory in vmstat and for cpu util , you could use that..thanks alot

grep -i ave|  awk '!( NR  % 12 ) {$0 = $0"\n"} 1'