Kangaroo Race

The country of Austria is known for its large kangaroo population. To stay in good shape, each kangaroo has its own athletics track for practicing for the Annual Austrian Pogostick Jumping Event.

Each athletics track consists of $n$ segments, each $1$ meter long. The segments are numbered from $1$ to $n$ in order. The track is cyclic, so segment $1$ comes right after segment $n$.

On each track, a kangaroo is located in one of the segments. The kangaroo can make a finite number of jumps. In each jump, if the kangaroo is in segment $y$, it jumps $y(y-1)$ segments ahead. Find the minimum number of jumps the kangaroo needs to reach segment $1$.

The first line contains an integer $k$ ($1 \leq k \leq 10^5$), the number of kangaroos. Each of the next $k$ lines contains two integers $n$ and $x$ ($1 \leq x \leq n \leq 10^{18}$), the number of segments on the track and the kangaroo's initial position on that track.

For each kangaroo, if it can reach segment $1$ in a finite number of jumps, output the minimum number of jumps needed. Otherwise, output impossible.

Intermediate values in your calculation may exceed the range of 64-bit integers. To store them, use __int128 in C++ or java.math.BigInteger in Java or Kotlin. Python integers have arbitrary size by default, so no special handling is needed.