0  1  2  3   
1  o  o  o
2  o  o  o   
3  o  o  o   
4        x

##</code><code>##


0  1  2  3   
1  o  o  o
2  o  o  o   
3  o  o  o   
4  a  b  x

##</code><code>##

(1,1,3)
(1,4,1)
(2,4,1)
(3,4,1)