The Blue Caterpillar Gives Advice
– What height do you wish to be? – asked the Caterpillar.
– Oh, it doesn't really matter, – Alice replied quickly. – It's just so bothersome to keep changing all the time...
– Take a bite from one side – you'll grow taller, from the other – you'll shrink!
– One side of what? – wondered Alice. – The other side of what?
– The mushroom, – answered the Caterpillar, as if reading her thoughts, and then vanished.
Alice's Adventures in Wonderland (translated by N.M. Demurova)
For a moment, Alice gazed thoughtfully at the mushroom, trying to figure out which side was which; the mushroom was round, which left her completely puzzled. Finally, she made up her mind: she grasped the mushroom with both hands and broke off a piece from each side. It turned out that if you bite from the piece in the left hand, you can grow by A inches, and if from the right – shrink by B inches.
Help Alice determine if she can become Y inches tall, given her current height is X inches.
Input
The first line of the input file contains four numbers: X, Y, A, B.
Here 0 ≤ |X|, |Y| ≤ 10^6, 0 ≤ |A|, |B| ≤ 10^2.
Output
Output a single integer – the minimum number of "bites" needed to reach the desired height, or –1 if it is impossible.