Problem Statement

The coordinate plane is covered with $2\times1$ tiles. The tiles are laid out according to the following rules:

• For an integer pair (i,j), the square $A _ {i,j}=\lbrace(x,y)\mid i\leq x\leq i+1\wedge j\leq y\leq j+1\rbrace$ is contained in one tile.
• When i+j is even, A _ {i,j} and A _ {i + 1,j} are contained in the same tile.

Tiles include their boundaries, and no two different tiles share a positive area.
Near the origin, the tiles are laid out as follows:

Takahashi starts at the point (S _ x+0.5,S _ y+0.5) on the coordinate plane.
He can repeat the following move as many times as he likes:

• Choose a direction (up, down, left, or right) and a positive integer n. Move n units in that direction.

Each time he enters a tile, he pays a toll of 1.
Find the minimum toll he must pay to reach the point (T _ x+0.5,T _ y+0.5).

Input

The input is given from Standard Input in the following format:
S _ x S _ y
T _ x T _ y

Output

Print the minimum toll Takahashi must pay.

Constraints

• $0\leq S _ x\leq2\times10 ^ {16}$
• $0\leq S _ y\leq2\times10 ^ {16}$
• $0\leq T _ x\leq2\times10 ^ {16}$
• $0\leq T _ y\leq2\times10 ^ {16}$
• All input values are integers.

Sample Input 1

5 0
2 5

Sample Output 1

5

For example, Takahashi can pay a toll of 5 by moving as follows:

• Move left by 1. Pay a toll of 0.
• Move up by 1. Pay a toll of 1.
• Move left by 1. Pay a toll of 0.
• Move up by 3. Pay a toll of 3.
• Move left by 1. Pay a toll of 0.
• Move up by 1. Pay a toll of 1.

It is impossible to reduce the toll to 4 or less, so print 5.

Sample Input 2

3 1
4 1

Sample Output 2

0

There are cases where no toll needs to be paid.

Sample Input 3

2552608206527595 5411232866732612
771856005518028 7206210729152763

Sample Output 3

1794977862420151

Note that the value to be output may exceed the range of a 32-bit integer.

见题面 Input 部分

见题面 Output 部分