Eating Soup

Description:

Input:

The only line contains two integers $$$n$$$ and $$$m$$$ ($$$2 \leq n \leq 1000$$$, $$$0 \leq m \leq n$$$) — the initial number of cats at the party and the number of cats who left the circle at the moment Katie observes, respectively.

Output:

Print a single integer — the maximum number of groups of cats at the moment Katie observes.

Sample Input:

7 4

Sample Output:

3

Sample Input:

6 2

Sample Output:

2

Sample Input:

3 0

Sample Output:

1

Sample Input:

2 2

Sample Output:

0

Note:

In the first example, originally there are $$$7$$$ cats sitting as shown below, creating a single group:

At the observed moment, $$$4$$$ cats have left the table. Suppose the cats $$$2$$$, $$$3$$$, $$$5$$$ and $$$7$$$ have left, then there are $$$3$$$ groups remaining. It is possible to show that it is the maximum possible number of groups remaining.

In the second example, there are $$$6$$$ cats sitting as shown below:

At the observed moment, $$$2$$$ cats have left the table. Suppose the cats numbered $$$3$$$ and $$$6$$$ left, then there will be $$$2$$$ groups remaining ($$$\{1, 2\}$$$ and $$$\{4, 5\}$$$). It is impossible to have more than $$$2$$$ groups of cats remaining.

In the third example, no cats have left, so there is $$$1$$$ group consisting of all cats.

In the fourth example, all cats have left the circle, so there are $$$0$$$ groups.