import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    static void printClosest(int arr[], int n) {
        int res_l = 0, res_r = 0;  // To store indexes of result pair

        int l = 0, r = n - 1, diff = Integer.MAX_VALUE;
        while (r > l) {
            if (Math.abs(arr[l] + arr[r]) < diff) {
                res_l = l;
                res_r = r;
                diff = Math.abs(arr[l] + arr[r]);
            }

            if (arr[l] + arr[r] > 0)
                r--;
            else
                l++;
        }
        System.out.println(diff);
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int[] a = new int[n];
        for (int a_i = 0; a_i < n; a_i++) {
            a[a_i] = in.nextInt();
        }

        printClosest(a, n);

    }
}