2 7
-6 -9 -4 -2 -10 -3 -6
-4 -8 -9 -1  -7 -5 -4
4 1 2 1 4 3 8
9 9 8 1 3 8 7
11 22


http://www.or.deis.unibo.it/kp/Chapter7.pdf Example 7.1