CF2184C Huge Pile

Andrei has a huge pile of $ n $ apples. He can divide the pile into two smaller piles: if there are $ x $ apples in the pile, he will get piles with $ \lfloor \frac{x}{2} \rfloor $ $ ^{\text{∗}} $ and $ \lceil \frac{x}{2} \rceil $ $ ^{\text{†}} $ apples. This division takes Andrei $ 1 $ minute. Andrei wants to eat $ k $ apples, but he doesn't want to count them at all. That is why he wants to obtain a pile that contains exactly $ k $ apples. Determine whether it is possible to achieve this by performing pile divisions. If it is possible, find the minimum possible time for Andrei to obtain a pile with exactly $ k $ apples. $ ^{\text{∗}} $ $ \lfloor \frac{x}{2} \rfloor $ — the largest integer $ \le \frac{x}{2} $ . $ ^{\text{†}} $ $ \lceil \frac{x}{2} \rceil $ — the smallest integer $ \ge \frac{x}{2} $ .

Each test consists of several test cases. The first line contains a single integer $ t $ $ (1 \le t \le 10^4) $ — the number of test cases. The following lines describe the test cases. In the only line of each test case, two integers $ n $ and $ k $ are given — the number of apples in the huge pile and the number of apples that Andrei wants to obtain in one pile $ (1 \le n, k \le 10^9) $ .

For each test case, output $ -1 $ if it is impossible to obtain a pile with exactly $ k $ apples. Otherwise, output the minimum possible time required to obtain such a pile.

In the first test case, after the first division, two piles of $ 5 $ apples will be created. If one of them is divided, it will result in piles with $ 2 $ and $ 3 $ apples, so the answer is $ 2 $ . In the second test case, if the pile is divided into two, it will result in piles with $ 5 $ and $ 6 $ apples, so the answer is $ 1 $ . In the third test case, it is only possible to obtain piles with $ 1 $ , $ 2 $ , $ 3 $ , $ 5 $ , $ 6 $ , $ 10 $ , $ 11 $ , or $ 21 $ apples, so the answer is $ -1 $ .