And so what we do is we use a special enzyme that adds a specific sequence of nucleotides onto the three prime end that we know. And so we add an enzyme called terminal transferase. And this catalyzes the addition of specific types of nucleotides. And so let's suppose we want to add a bunch of deoxyguanosine triphosphates so Dgtps. And so after step four, we essentially add a polygtail to the three prime of this complementary DNA molecule. And now we know exactly what the sequence on the three prime end here is.