Problem Statement

You are given positive integers $N$ and $M$.
Find the smallest positive integer $X$ that satisfies both of the conditions below, or print $\-1$ if there is no such integer.

• $X$ can be represented as the product of two integers $a$ and $b$ between $1$ and $N$, inclusive. Here, $a$ and $b$ may be the same.
• $X$ is at least $M$.

Constraints

• $1\\leq N\\leq 10^{12}$
• $1\\leq M\\leq 10^{12}$
• $N$ and $M$ are integers.

Input

The input is given from Standard Input in the following format:

$N$ $M$

Output

Print the smallest positive integer $X$ that satisfies both of the conditions, or $\-1$ if there is no such integer.

Sample Input 1

5 7

Sample Output 1

8

First, $7$ cannot be represented as the product of two integers between $1$ and $5$.
Second, $8$ can be represented as the product of two integers between $1$ and $5$, such as $8=2\\times 4$.

Thus, you should print $8$.

Sample Input 2

2 5

Sample Output 2

-1

Since $1\\times 1=1$, $1\\times 2=2$, $2\\times 1=2$, and $2\\times 2=4$, only $1$, $2$, and $4$ can be represented as the product of two integers between $1$ and $2$, so no number greater than or equal to $5$ can be represented as the product of two such integers.
Thus, you should print $\-1$.

Sample Input 3

100000 10000000000

Sample Output 3

10000000000

For $a=b=100000$ $(=10^5)$, the product of $a$ and $b$ is $10000000000$ $(=10^{10})$, which is the answer.
Note that the answer may not fit into a $32$-bit integer type.