B=[4 5 6];
C=[7 8 9];
a1=nchoosek(1:3,2);
[m n]=size(a1);
r=[];
for i=1:m
for j=1:m
for k=1:m
r=[r;A(a1(i,:)) B(a1(j,:)) C(a1(k,:))];
end