CF301A.Yaroslav and Sequence

Yaroslav has an array, consisting of (2·n - 1) integers. In a single operation Yaroslav can change the sign of exactly n elements in the array. In other words, in one operation Yaroslav can select exactly n array elements, and multiply each of them by -1.

Yaroslav is now wondering: what maximum sum of array elements can be obtained if it is allowed to perform any number of described operations?

Help Yaroslav.

亚罗斯拉夫有一个由 $2\cdot n - 1$ 个整数组成的数组。在一次操作中，亚罗斯拉夫可以恰好改变数组中 $n$ 个元素的符号。换言之，在一次操作中，亚罗斯拉夫可以恰好选择 $n$ 个数组元素，并将它们各自乘以 $-1$。

亚罗斯拉夫现在想知道：若允许执行任意次数的上述操作，数组元素之和的最大值是多少？

请帮助亚罗斯拉夫。

The first line contains an integer n (2 ≤ n ≤ 100). The second line contains (2·n - 1) integers — the array elements. The array elements do not exceed 1000 in their absolute value.

第一行包含一个整数 $n$（$2 \leq n \leq 100$）。第二行包含 $2n - 1$ 个整数——数组的元素。数组元素的绝对值不超过 $1000$。

In a single line print the answer to the problem — the maximum sum that Yaroslav can get.

在一行中输出问题的答案——Yaroslav 能得到的最大和。

In the first sample you do not need to change anything. The sum of elements equals 150.

In the second sample you need to change the sign of the first two elements. Then we get the sum of the elements equal to 100.

在第一个样例中，您无需进行任何更改。元素之和等于 $150$。

在第二个样例中，您需要将前两个元素的符号取反。然后，元素之和等于 $100$。