Extracting rows based based on criteria from two columns

A= [1 1 4; 
    1 2 6; 
    1 3 9; 
    1 4 10;
    2 1 12; 
    2 2 15; 
    2 3 20;
    2 4 45]
I want to extract rows from the matrix as follows: For each consecutive number in the first column extract rows using increment of 2 in the second column. The result will be:

A=   [1 2 6; 
      1 4 10; 
      2 2 15; 
      2 4 45]

Answer 1

[KSSV]

iwant = A(2:2:end,:)