Problem Statement

The king piece in shogi can move $1$ square in any of $8$ directions.
When it is at $(0,0)$, it can move to any of $(-1,1),(0,1),(1,1),(-1,0),(1,0),(-1,-1),(0,-1),(1,-1)$.
The king is currently on the square $(0,0)$.
You want to move it to the square $(x,y)$ as quickly as possible.
However, an allied pawn is at $(x_2,y_2)$ and is in the way.
Find the minimum number of moves to go from $(0,0)$ to $(x,y)$.
Note that the pawn cannot be moved.
This shogi board is infinitely large, and squares with negative coordinates also exist. (Negative coordinates are not given in the input.)

Input

$x \ y$
$x_2 \ y_2$

Line $1$ contains the coordinates of the destination square, separated by a space.
Line $2$ contains the coordinates of the square where the pawn is, separated by a space.

$0 \le x,y,x_2,y_2 \le 10^9$
$(0,0),(x,y),(x_2,y_2)$ are all distinct.

Output

Output the minimum number of moves to reach $(x,y)$.

Sample

1 1
1 0

1

10 1
1 0

10