Time Travelling Temperatures
Hello from the future. I am a time traveller. You would think that in the future we have agreed to use a single scale for measuring temperature. This is not so. In fact, we have all sorts of scales now. All the big brands have made their own. This is a bit confusing. Please help me figure it out. In my day to day work I have to relate to two different scales $A$ and $B$. Help me find a temperature where the two scales are the same, so I don’t have to worry about it.
Input
Input consists of two spaceseparated integers, $X$ and $Y$. $X$ is the point on $B$ where $A$ is zero. $Y$ is the number of degrees in $B$ that equal a change of a single degree in $A$.
Output
Output the temperature where both scales are the same. This number must have an absolute or relative error of at most $10^{6}$. If no such temperature exists, output “IMPOSSIBLE” (without the quotes) instead. If more than one such point exists, output “ALL GOOD” (without the quotes) instead.
Limits

$100 \leq X \leq 100$

$1 \leq Y \leq 100$
Sample Input 1  Sample Output 1 

32 2 
32 
Sample Input 2  Sample Output 2 

1 3 
0.500000000 