[CF 치고 알고리즘 배우 기 - 1 성급] CodeForces 318 A (물 문제)

[CF 프로필]
제출 링크:http://codeforces.com/problemset/problem/318/A
제목:
C - Even Odds
Time Limit:1000MS     Memory Limit:262144KB     64bit IO Format:%I64d & %I64u
Submit 
Status
Description
Being a nonconformist, Volodya is displeased with the current state of things, particularly with the order of natural numbers (natural number is positive integer number). He is determined to rearrange them. But there are too many natural numbers, so Volodya decided to start with the first n. He writes down the following sequence of numbers: firstly all odd integers from 1 to n (in ascending order), then all even integers from 1 to n (also in ascending order). Help our hero to find out which number will stand at the position number k.
Input
The only line of input contains integers n and k (1 ≤ k ≤ n ≤ 1012).
Please, do not use the %lld specifier to read or write 64-bit integers in C++. It is preferred to use the cin, cout streams or the %I64dspecifier.
Output
Print the number that will stand at the position number k after Volodya's manipulations.
Sample Input
Input

10 3

Output

5

Input

7 7

Output

6

Hint
In the first sample Volodya's sequence will look like this: {1, 3, 5, 7, 9, 2, 4, 6, 8, 10}. The third place in the sequence is therefore occupied by the number 5.
제목 의 대의:
    홀수 가 앞 에 있 고 짝수 가 뒤에 있 으 니 몇 번 째 숫자 가 무엇 인지 물 어보 세 요.오 랜 만 에 문 제 를 풀 었 으 니 서명 해라!
코드:

#include 
#include 
#include 
#include  
#include 
#include 
#include 
using namespace std;
#define inf 1e9
#define LL long long
#define ULL unsigned long long

int main()
{
    long long a,b,mid;
    scanf("%I64d%I64d",&a,&b);
    mid=(a+1)/2;
    if(b<=mid)
      printf("%I64d
",b*2-1);
    else
      printf("%I64d
",(b-mid)*2);
	return 0;
}