The entire superset of all known and potentially feasable sequences of viable DNA sets, just to be conservative. The entire Time of our universe's existence, using the most optimistic longevity value. The most optimistic calculation of the numbers of viable life-sustaining environments in our universe, and the most optimistic number of possible molecules in said environments...all while giving each molecule the theoretical ability to self-form into a viable DNA sequence.
The link that I gave you gives the math for all of the above, along with the highest probability for such a hit occuring given that much time in that many worlds: 0 (rounded to the nearest 185th decimal place).