Since it seems that the winner is not here, I will explain this riddle.

1. So we have a signature, we should check for weak K1, use kangaroos of course
What's the range for search? Use a hint from the message, 80bit. Fails, it seems K1 is strong.

2. Remember that I posted another signature, take K2, may be K1==K2? No.
So if we have both strong K1 and K2, what it can be?
Remember that ECDSA Signature is vulnerable not only when K1==K2 but also if we know that
K1 has some relation with K2, for example, K2=K1+1 (the simplest case).
How to check it? Remember that R1=G*K1 and R2=G*K2 and we have these R1 and R2 points in signatures, so we can substract: PntDiff = R1 - R2
(and also try R2 - R1) and check if it's G. It's not G, ok, may be the difference is not 1 but more?
We should try to solve PntDiff (both variants) with kangaroos. What's the range? Same, 80bits. And we can solve it, so now we have delta_K.

3. Now calculate, google or ask chatbot to get the formula:
pk = ((delta_k * s1 * s2) + (z2 * s1) - (z1 * s2)) / (r1 * s2 - r2 * s1) [mod n]

That's all!