Package for this problem was not updated by the problem writer or Codeforces administration after we’ve upgraded the judging servers. To adjust the time limit constraint, solution execution time will be multiplied by 2. For example, if your solution works for 400 ms on judging servers, then value 800 ms will be displayed and used to determine the verdict.

Virtual contest is a way to take part in past contest, as close as possible to participation on time. It is supported only ACM-ICPC mode for virtual contests.
If you've seen these problems, a virtual contest is not for you - solve these problems in the archive.
If you just want to solve some problem from a contest, a virtual contest is not for you - solve this problem in the archive.
Never use someone else's code, read the tutorials or communicate with other person during a virtual contest.

No tag edit access

A. Exams

time limit per test

2 secondsmemory limit per test

256 megabytesinput

standard inputoutput

standard outputOne day the Codeforces round author sat exams. He had *n* exams and he needed to get an integer from 2 to 5 for each exam. He will have to re-sit each failed exam, i.e. the exam that gets mark 2.

The author would need to spend too much time and effort to make the sum of his marks strictly more than *k*. That could have spoilt the Codeforces round. On the other hand, if the sum of his marks is strictly less than *k*, the author's mum won't be pleased at all.

The Codeforces authors are very smart and they always get the mark they choose themselves. Also, the Codeforces authors just hate re-sitting exams.

Help the author and find the minimum number of exams he will have to re-sit if he passes the exams in the way that makes the sum of marks for all *n* exams equal exactly *k*.

Input

The single input line contains space-separated integers *n* and *k* (1 ≤ *n* ≤ 50, 1 ≤ *k* ≤ 250) — the number of exams and the required sum of marks.

It is guaranteed that there exists a way to pass *n* exams in the way that makes the sum of marks equal exactly *k*.

Output

Print the single number — the minimum number of exams that the author will get a 2 for, considering that the sum of marks for all exams must equal *k*.

Examples

Input

4 8

Output

4

Input

4 10

Output

2

Input

1 3

Output

0

Note

In the first sample the author has to get a 2 for all his exams.

In the second sample he should get a 3 for two exams and a 2 for two more.

In the third sample he should get a 3 for one exam.

Codeforces (c) Copyright 2010-2017 Mike Mirzayanov

The only programming contests Web 2.0 platform

Server time: May/28/2017 00:15:05 (c4).

Desktop version, switch to mobile version.
User lists

Name |
---|