201121: [AtCoder]ARC112 B - -- - B

Problem Statement

Snuke has come to Seisu-ya (integer shop) with an integer $B$ in his hand. In Seiyu-ya, you can exchange your integer for another integer by paying money.

More specifically, you can use the following two services any number of times in any order:

• Pay $1$ yen (the currency of Japan) to multiply your integer by $-1$.
• Pay $2$ yen to subtract $1$ from your integer.

How many integers are there that Snuke can get for at most $C$ yen?

Constraints

• $-10^{18}\le B \le 10^{18}$
• $1\le C \le 10^{18}$
• All values in input are integers.

Input

Input is given from Standard Input in the following format:

$B$ $C$

Output

Print the answer.

Sample Input 1

11 2

Sample Output 1

3

There are three numbers that Snuke can get: $-11$, $10$, and $11$, as follows:

• by doing nothing, he can get $11$ for $0$ yen;
• by multiplying $11$ by $-1$, he can get $-11$ for $1$ yen;
• by subtracting $1$ from $11$, he can get $10$ for $2$ yen.

Sample Input 2

0 4

Sample Output 2

4

There are four numbers that Snuke can get: $-2$, $-1$, $0$, and $1$, as follows:

• by doing nothing, he can get $0$ for $0$ yen;
• by subtracting $1$ from $0$, he can get $-1$ for $2$ yen;
• by subtracting $1$ from $0$ and then multiplying by $-1$, he can get $1$ for $3$ yen;
• by subtracting $1$ from $0$ and then subtracting $1$ again, he can get $-2$ for $4$ yen.

Sample Input 3

112 20210213

Sample Output 3

20210436

Sample Input 4

-211 1000000000000000000

Sample Output 4

1000000000000000422