Factors Problem

Problem Background

Special for beginners, ^_^

Problem Description

Given two positive integers $N$ and $M$, find the smallest positive integer $a$ such that both $a$ and $(M - a)$ are factors of $N$.

Input Format

Two integers $N$ and $M$. $N$ does not exceed $1{,}000{,}000$.

Output Format

Output one integer $a$ as the result. If no positive integer satisfying the condition exists for a given case, output $-1$ in the corresponding line.

Sample Input

35 10

Sample Output

5

Constraints

1s, 1024KiB for each test case.