ABC105C

https://gyazo.com/138fd19d56e29837bebffb7acca1e9cf

Thoughts.

1 when 1

110 at 2

Since it is 4-2

111 at 3

Since 2+1

100 at 4

101 at 5

When I was 6...

11010

4+2 is 8-2 and 8 is 16-8.

Separate odd and even digits

$ N = S_0 \times (-2)^0 + S_1 \times (-2)^1 + ... + S_k \times (-2)^k

$ = \sum_{i \in (0,2,4,...)} S_i 2^i - \sum_{i \in (1, 3,...)} S_i 2^i

$ = S_0 + \sum_{i \in (2,4,...)} S_i 2^i - \sum_{i \in (1, 3,...)} S_i 2^i

mod 4, where the first term is S0, the second term is 0, and the third term is 2S2

Therefore, the remainder divided by 4 determines the last two digits.

Divide the remainder by four, and the same thing can be repeated.

Repeat until it reaches 0.

logarithmic order

Official Explanation

Decide from the bottom in the same way.

---