Now, because to break this double bond, we actually have to input a certain amount of energy. And because the energy change symbol is given by the Greek symbol delta, this triangle, the double bond, is represented with the delta symbol. And to basically describe the position, the number of that double bond with respect to this reference point, carbon number one. All we have to do is we have to mark that triangle with a numerical SuperScript. So let's suppose we want to describe this particular bond here. So this atom is carbon four.