function    value=prodV(B)
%  multiplication B*V
B=sparse(B);
n=size(B,2);
m=size(B,1);
n1=n-1;
y=-1/sqrt(n);
x=-1/(n+sqrt(n));
value=sparse(  y*(B(:,1)*sparse(ones(1,n1)))+(x+1)*B(:,2:end) );
