Folding a Rectangle

You have a rectangular sheet of paper whose sides are $W$ and $H$. You want to fold it several times until it becomes a rectangle whose sides are $w$ and $h$.

Every fold line is parallel to a side of the rectangle, and the shape after a fold is again a rectangle. Folding a side of length $L$ at distance $x$ from one of its ends ($0 < x < L$) leaves that side with the longer of the two pieces, $\max(x, L-x)$, and the other side keeps its length.

The finished rectangle may be turned around. Any orientation whose sides are $w$ and $h$ counts.

Write a program that computes the minimum number of folds.

The first line contains the two side lengths $W$ and $H$ of the starting rectangle. The second line contains the two side lengths $w$ and $h$ of the target rectangle. ($1 \le W, H, w, h \le 10^9$)

Print the minimum number of folds that turns the starting rectangle into the target rectangle. Print -1 when it is impossible.