CF570B.Simple Game

One day Misha and Andrew were playing a very simple game. First, each player chooses an integer in the range from 1 to n. Let's assume that Misha chose number m, and Andrew chose number a.

Then, by using a random generator they choose a random integer c in the range between 1 and n (any integer from 1 to n is chosen with the same probability), after which the winner is the player, whose number was closer to c. The boys agreed that if m and a are located on the same distance from c, Misha wins.

Andrew wants to win very much, so he asks you to help him. You know the number selected by Misha, and number n. You need to determine which value of a Andrew must choose, so that the probability of his victory is the highest possible.

More formally, you need to find such integer a (1 ≤ a ≤ n), that the probability that is maximal, where c is the equiprobably chosen integer from 1 to n (inclusive).

有一天，米沙和安德鲁玩了一个非常简单的游戏。首先，每位玩家在 $1$ 到 $n$ 的范围内选择一个整数。假设米沙选择了数字 $m$，而安德鲁选择了数字 $a$。

接着，他们利用一个随机数生成器，在 $1$ 到 $n$ 之间随机选取一个整数 $c$（即从 $1$ 到 $n$ 中任一整数被选中的概率均等），之后获胜者为所选数字离 $c$ 更近的那位玩家。两人约定：若 $m$ 和 $a$ 到 $c$ 的距离相等，则米沙获胜。

安德鲁非常想赢，因此他请你帮忙。你已知米沙所选的数字 $m$ 以及 $n$ 的值。你需要确定安德鲁应选择哪个值 $a$，才能使其获胜的概率最大化。

更形式化地说，你需要找出满足 $1 \leq a \leq n$ 的整数 $a$，使得下式成立的概率最大：

其中 $c$ 是在 $1$ 到 $n$（含端点）之间等概率选取的整数。

The first line contains two integers n and m (1 ≤ m ≤ n ≤ 109) — the range of numbers in the game, and the number selected by Misha respectively.

第一行包含两个整数 $n$ 和 $m$（$1 \leq m \leq n \leq 10^9$）—— 分别表示游戏中数字的范围，以及米沙所选择的数字。

Print a single number — such value a, that probability that Andrew wins is the highest. If there are multiple such values, print the minimum of them.

输出一个数字——即使得安德鲁获胜概率最大的值 $a$。如果存在多个这样的值，则输出其中最小的一个。

In the first sample test: Andrew wins if c is equal to 2 or 3. The probability that Andrew wins is 2 / 3. If Andrew chooses a = 3, the probability of winning will be 1 / 3. If a = 1, the probability of winning is 0.

In the second sample test: Andrew wins if c is equal to 1 and 2. The probability that Andrew wins is 1 / 2. For other choices of a the probability of winning is less.

在第一个样例测试中：当 $c$ 等于 2 或 3 时，Andrew 获胜。Andrew 获胜的概率为 $2/3$。若 Andrew 选择 $a = 3$，则获胜概率为 $1/3$；若 $a = 1$，则获胜概率为 $0$。

在第二个样例测试中：当 $c$ 等于 1 和 2 时，Andrew 获胜。Andrew 获胜的概率为 $1/2$。对于其他 $a$ 的取值，获胜概率均更小。