import java.util.Arrays;
import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] a = new int[n];
        for(int i=0;i<n;i++) {
            a[i] = sc.nextInt();
        }
        Arrays.sort(a);
        System.out.println(2*a[n-1]);    // 输出最高峰的2倍，1上 1下
        
    }

}