C1 = sparse(13,13);
C1(1,2)=1;
C1(1,3)=1;
C1(2,4)=1;
C1(2,5)=1;
C1(3,6)=1;
C1(3,7)=1;
C1(4,2)=1;
C1(4,8)=1;
C1(5,9)=1;
C1(5,10)=1;
C1(6,11)=1;
C1(6,12)=1;
C1(7,3)=1;
C1(7,13)=1;