function U=sceltabis(Y)
  
  % given an array of columns Y, the program gives a matrix U whose rows are obtained by taking an element a1 from Y(1), then an element from  Y(2) different form a1 and so on

  U=cell2mat(Y(1,1));
  for i=2:size(Y,2)
	  U=scelta(U,cell2mat(Y(1,i)));
	  end