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

public class Solution {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int[] a = new int[n];
        int min = 0;
        
        for(int a_i=0; a_i < n; a_i++){
            a[a_i] = in.nextInt();
            
            if(a_i > 0)
                {
                    for(int j=0; j<a_i; j++)
                        {
                            if(min > Math.abs(a[j]+a[a_i]))
                                min = Math.abs(a[j]+a[a_i]);
                    }
            }
            else
                min = a[a_i];
        }
        System.out.print(min);
    }
     
                                          
    
}