import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] c = new int[n];
		for (int i = 0; i < n; i++) {
			c[i] = sc.nextInt();
		}
		sc.close();

		int l = Math.min(c[0], 0);
		int r = Math.max(c[n - 1], 0);
		int ans = -l * 2 + r * 2;
		System.out.println(ans);
	}
}