title: how to skip specific lines in awk and print the remaining
body: <p>how can I read only lines: 3,9,12, 15 from the  file containing the ff lines.
  The idea is whenever I get x and  y , I wanted to print the last line among lines containing x and y.
  What I meant is , for example , if I have awk script like : BEGIN { name = $2; value=$3; } { if(name == x &amp;&amp; value==y &amp;&amp; the scan reaches at lines 3, 9, 12 and 15) printf("hello world") }. what expression can I use instead of "the scan reaches at lines 3, 9 12 and 15"</p>
  
  <pre><code>1 x y
  2 x y 
  3 x y 
  4 a d
  5 e f
  6 x y
  7 x y
  8 x y
  9 x y
  10 g f
  11 x y
  12 x y
  13 p r
  14 w c
  15 x y
  16 a z
  </code></pre>