Eternal Youth

My birthday is coming up. I have been getting older and I wanted to feel young again, so I found a way to look younger. Pick a suitable base $b$, write my age in that base, and the number looks smaller. My age is 32 in decimal, but in base 16 it is only 20.

The base cannot be picked freely. If the age written in base $b$ contains a single position that is not one of the digits 0 to 9, everybody sees at once that I am cheating and the whole trick is useless.

A value that looks too small is a problem as well. If the written value is far too small, that is obviously cheating too. So I fixed a lower bound $l$.

You are given my age $y$ and the lower bound $l$. Find the largest $b$ such that every position of $y$ written in base $b$ is one of the digits 0 to 9, and that representation read as a decimal number is at least $l$.

One line with two integers $y$ and $l$, written in decimal. ($10 \le y \le 10^{18}$, $10 \le l \le y$)

Print the largest $b$ described above.