using System;

public class Hello
{
    static void Main()
    {
        var n = int.Parse(Console.ReadLine().Trim());
        string[] line = Console.ReadLine().Trim().Split(' ');
        var a = Array.ConvertAll(line, int.Parse);
        getAns(n, a);
    }

    static void getAns(int n, int[] a)
    {
        var ans = 0;
        if (a[0] >= 0) ans = 2 * a[n - 1];
        else if (a[n - 1] <= 0) ans = -a[0] * 2;
        else ans = -a[0] * 2 + a[n - 1] * 2;
        Console.WriteLine(ans);
    }
}