Berland Square

2000ms

262144K

Description:

Last year the world's largest square was built in Berland. It is known that the square can be represented as an infinite plane with an introduced Cartesian system of coordinates. On that square two sets of concentric circles were painted. Let's call the set of concentric circles with radii 1, 2, ..., K and the center in the point (z, 0) a (K, z)-set. Thus, on the square were painted a (N, x)-set and a (M, y)-set. You have to find out how many parts those sets divided the square into.

Input:

The first line contains integers N, x, M, y. (1 ≤ N, M ≤ 100000, - 100000 ≤ x, y ≤ 100000, x ≠ y).

Output:

Print the sought number of parts.

Sample Input:

1 0 1 1

Sample Output:

Sample Input:

1 0 1 2

Sample Output:

Sample Input:

3 3 4 7

Sample Output:

Note:

Picture for the third sample:

$\text{[math]}$

Informação

Provedor Codeforces

Código CF40C