Problem:
Score : 700 points

Problem Statement

We have N gemstones labeled 1 through N.

You can perform the following operation any number of times (possibly zero).

Select a positive integer x, and smash all the gems labeled with multiples of x.

Then, for each i, if the gem labeled i remains without getting smashed, you will receive a_i yen (the currency of Japan).
However, a_i may be negative, in which case you will be charged money.

By optimally performing the operation, how much yen can you earn?

Constraints

All input values are integers.

1 \leq N \leq 100

|a_i| \leq 10^9

Input

Input is given from Standard Input in the following format:

N
a_1 a_2 ... a_N

Output

Print the maximum amount of money that can be earned.

Sample Input 1

6
1 2 -6 4 5 3

Sample Output 1

12

It is optimal to smash Gem 3 and 6.

Sample Input 2

6
100 -100 -100 -100 100 -100

Sample Output 2

200

Sample Input 3

5
-1 -2 -3 -4 -5

Sample Output 3

0

It is optimal to smash all the gems.

Sample Input 4

2
-1000 100000

Sample Output 4

99000

Solution in C# (Mono 4.6.2.0) (judge verdict: Time Limit Exceeded)

using System;
using System.Collections.Generic;
using System.Linq;
// もうむり 
namespace AtCoder
{
    public class AtCoder20171111E
    {
        static void Main(string[] args)
        {
            var s1 = Console.ReadLine();
            var s2 = Console.ReadLine();
            
            Console.WriteLine(funcMain(s1,s2));
 
            Console.ReadKey();
        }
 
        static public string funcMain(string arg1, string arg2)
        {
            long ret = 0;
            int N = int.Parse(arg1);
            var list1 = arg2.Split().Select(f => long.Parse(f)).ToList();
            for (int i = N; i > 0; i--) {
                var list2 = list1.Select((f, index) => ((index + 1) % i == 0) ? 0 : f).ToList();
                if (list2.Sum() >= list1.Sum()) {
                    list1 = list2;
                    i = N; // これか！？
                }
            }
            ret = list1.Sum();
            return ret.ToString();
        }
    }
}