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: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Linq;
using System.IO;
using System.Text;
using System.Globalization;
using System.Diagnostics;
using static System.Console;
//using System.Numerics;
//using static System.Math;

class Program
{
    static void Main()
    {
        //SetOut(new StreamWriter(OpenStandardOutput()) { AutoFlush = false });
        new Program().solve();
        Out.Flush();
    }
    Scanner cin = new Scanner();
    readonly int[] dd = { 0, 1, 0, -1, 0 }; //→↓←↑
    readonly int mod = 1000000007;


    class Pair<T, U> : IComparable<Pair<T, U>> where T : IComparable<T> where U : IComparable<U>
    {
        public T f;
        public U s;
        public Pair(T f, U s)
        {
            this.f = f;
            this.s = s;
        }
        public int CompareTo(Pair<T, U> a)
        {
            return f.CompareTo(a.f) != 0 ? f.CompareTo(a.f) : s.CompareTo(a.s);
        }
        public override string ToString()
        {
            return f + " " + s;
        }
    }

    void solve()
    {
        int N = cin.nextint;
        var A = new long[N + 1];

        for (int i = 1; i <= N; i++)
        {
            var k = cin.nextlong;
            A[i] = k;
            if (i >= N / 2 + 1 && A[i] < 0) A[i] = 0;
        }



        for (int i = N; i >= 1; i--)
        {
            long sum = 0;
            int j = i;
            int bai = 1;
            while (j <= N)
            {
                sum += A[j];
                bai++;
                j = i * bai;
                //WriteLine(i + " " + j);
            }

            if (sum < 0)
            {
                j = i;
                if (A[j] < 0)
                {
                    j = i;
                    bai = 1;
                    while (j <= N)
                    {
                        A[j] = 0;
                        bai++;
                        j = i * bai;
                    }
                }
                else
                {

                }

            }
        }
        //WriteLine(string.Join(" ", A));



        long ans = 0;
        for (int i = 1; i <= N; i++)
        {
            ans += A[i];
        }
        WriteLine(Math.Max(ans, 0));
    }

}

class Scanner
{
    string[] s; int i;
    char[] cs = new char[] { ' ' };
    public Scanner() { s = new string[0]; i = 0; }
    public string[] scan { get { return ReadLine().Split(); } }
    public int[] scanint { get { return Array.ConvertAll(scan, int.Parse); } }
    public long[] scanlong { get { return Array.ConvertAll(scan, long.Parse); } }
    public double[] scandouble { get { return Array.ConvertAll(scan, double.Parse); } }
    public string next
    {
        get
        {
            if (i < s.Length) return s[i++];
            string st = ReadLine();
            while (st == "") st = ReadLine();
            s = st.Split(cs, StringSplitOptions.RemoveEmptyEntries);
            i = 0;
            return next;
        }
    }
    public int nextint { get { return int.Parse(next); } }
    public long nextlong { get { return long.Parse(next); } }
    public double nextdouble { get { return double.Parse(next); } }
}