function merge( a, b : tree ) : tree;
	begin
	if a = nil then merge := b
	else if b = nil then merge := a
	else if a^.k > b^.k then begin
		a^.right := merge( a^.right, b );
		fixdist( a );
		merge := a
		end
	else	begin
		b^.right := merge( a, b^.right );
		fixdist( b );
		merge := b
		end
	end;

	procedure delete ( var pq : tree );
	begin
	if pq = nil then Error {*** delete on an empty queue ***}
	else	pq := merge( pq^.left, pq^.right )
	end;