P = sparse(13,13);
P(1,2)=0.5;
P(1,3)=0.5;
P(2,4)=0.5;
P(2,5)=0.5;
P(3,6)=0.5;
P(3,7)=0.5;
P(4,2)=0.5;
P(4,8)=0.5;
P(5,9)=0.5;
P(5,10)=0.5;
P(6,11)=0.5;
P(6,12)=0.5;
P(7,3)=0.5;
P(7,13)=0.5;
P(8,8)=1;
P(9,9)=1;
P(10,10)=1;
P(11,11)=1;
P(12,12)=1;
P(13,13)=1;