# Transform

One can transform $$x$$ into $$x + d$$ if $$d$$ is divisor of $$x$$. Find out the minimum number of steps to transform $$a$$ into $$b$$.

## Input

Two integers $$a$$ and $$b$$.

($$1 \leq a, b \leq 10^5$$)

## Output

The only integer denotes the minimum number of steps. Print $$-1$$ if impossible.

## Sample input

1 6

## Sample output

3

## Note

$$1 \to 2 \to 4 \to 6$$ or $$1 \to 2 \to 3 \to 6$$.

## Source

Contest #3 on acdream oj by ftiasch