cf 570B B. Simple Game(构造)

B. Simple Game

time limit per test

1 second

memory limit per test

256 megabytes

input

standard input

output

standard output

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 1and 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).

Input

/*************************************************************************
    > File Name: code/cf/#316/B.cpp
    > Author: 111qqz
    > Email: rkz2013@126.com 
    > Created Time: 2015年08月14日 星期五 00时36分16秒
 ************************************************************************/

#include<iostream>
#include<iomanip>
#include<cstdio>
#include<algorithm>
#include<cmath>
#include<cstring>
#include<string>
#include<map>
#include<set>
#include<queue>
#include<vector>
#include<stack>
#define y0 abc111qqz
#define y1 hust111qqz
#define yn hez111qqz
#define j1 cute111qqz
#define tm crazy111qqz
#define lr dying111qqz
using namespace std;
#define REP(i, n) for (int i=0;i<int(n);++i)  
typedef long long LL;
typedef unsigned long long ULL;
const int inf = 0x7fffffff;
int n,m;
int main()
{
    cin>>n>>m;
    if (n==1&&m==1)
    {
    cout<<1<<endl;
    return 0;
    }
    if (n%2==0)
    {
    if (m<=n/2)
    {
        cout<<m+1<<endl;
    }
    else
    {
        cout<<m-1<<endl;
    }
    }
    else
    {
    if (m>=(n+1)/2)
    {
        cout<<m-1<<endl;
    }
    else
    {
        cout<<m+1<<endl;
    }
    }
  
    return 0;
}

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.

Output

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.

Sample test(s)

input

3 1

output

2

input

4 3

output

2

Note

In the first sample test: Andrew wins if c is equal to 2 or 3. The probability that Andrew wins is2 / 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.

题意说得很清楚．

比较坑的是１　１这组数据

如果不特殊考虑，就会得到答案０

但是０不在范围内．

所以１　１　的答案也是１

虽然这样赢得的概率是０，但是是唯一能选择的情况．