function a=convs(varargin)
a=1; i=1;
while i<=length(varargin)
   k=1; a1=varargin{i}; i=i+1;
   if i<=length(varargin)
      if isa(varargin{i},'cell'), 
         k=varargin{i}{1}; i=i+1; 
      end 
   end
   for j=1:k, a=conv(a,a1); end
end