Codeforces Round #188 (Div. 2) / 318A Even Odds(简单数学)

A. Even Odds

http://codeforces.com/problemset/problem/318/A

time limit per test

1 second

memory limit per test

256 megabytes

input

standard input

output

standard output

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 test(s)

input

10 3

output

5

input

7 7

output

6

水。

完整代码：

/*30ms,0KB*/

#include<cstdio>

int main()
{
	__int64 n, k;
	scanf("%I64d%I64d", &n, &k);
	if (n & 1)
	{
		if (k > (n >> 1) + 1)
		{
			k -= (n >> 1) + 1;
			printf("%I64d", k << 1);
		}
		else
			printf("%I64d", (k << 1) - 1);
	}
	else
	{
		if (k > (n >> 1))
		{
			k -= n >> 1;
			printf("%I64d", k << 1);
		}
		else
			printf("%I64d", (k << 1) - 1);
	}
	return 0;
}