4  4
3  1  2  1  c
-1  1  1  1  b
 1 -1  1  1  b
 1  1 -1  1  b
 1  1  1 -1  b

1  2a  1  1  b
2  1  1  1  1
2  3  2  1 
3  3  1
4  1
4