Side of the square

Find the integer length of the square, which can be obtained from the two rectangles a x b and c x d, cut them into rectangles and then folded so as to obtain the greatest possible area of the square.

Input

In one row there are four real numbers a, b, c, d. The area of each rectangle is less than 2·10⁹.

Output

Derive a single number - the educated side of the square.