Problem Statement

There is an infinite two-dimensional grid, and we have a piece called Super Ryuma at square (r_1, c_1). (Ryu means dragon and Ma means horse.)
In one move, the piece can go to one of the squares shown below:

More formally, when Super Ryuma is at square (a, b), it can go to square (c, d) such that at least one of the following holds:

• a + b = c + d
• a - b = c - d
• $|a - c| + |b - d| \le 3$

Find the minimum number of moves needed for the piece to reach (r_2, c_2) from (r_1, c_1).

Input

Input is given from Standard Input in the following format:
r_1 c_1
r_2 c_2

Output

Print the minimum number of moves needed for Super Ryuma to reach (r_2, c_2) from (r_1, c_1).

Constraints

• All values in input are integers.
• $1 \le r_1, c_1, r_2, c_2 \le 10^9$

Sample Input 1

1 1
5 6

Sample Output 1

2

We need two moves - for example$, (1, 1) \rightarrow (5, 5) \rightarrow (5, 6)$.

Sample Input 2

1 1
1 200001

Sample Output 2

2

We need two moves - for example$, (1, 1) \rightarrow (100001, 100001) \rightarrow (1, 200001)$.

Sample Input 3

2 3
998244353 998244853

Sample Output 3

3

We need three moves - for example$, (2, 3) \rightarrow (3, 3) \rightarrow (-247, 253) \rightarrow (998244353, 998244853)$.

Sample Input 4

1 1
1 1

Sample Output 4

0

见题面 Input 部分

见题面 Output 部分