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 Ruby (2.3.3) (judge verdict: Wrong Answer)

def score(n, arr)
  sum = 0
  min_sum = 0
  ind = arr.size
  arr.reverse.each_with_index do |x, i|
    if (arr.size - i) % n == 0
      sum += x
      if min_sum > sum
        ind = arr.size - i - 1
        min_sum = sum
      end
    end
  end
  # p [n, ind, min_sum].join(",")
  if min_sum < 0
    while ind < arr.size
      arr[ind] = 0
      ind += n
    end
  end
  # return min_sum
end

N = gets.to_i
num = gets.split.map(&:to_i)
# score = num.inject(:+)

if N == 1
  if num[0] >= 0
    puts num[0]
  else
    puts 0
  end
else
  min_score = 0
  (2..num.size).to_a.reverse.each do |i|
    # min_score = [min_score, score(i, num)].min
    score(i,num)
  end
  # p num
  puts ([num.inject(:+), 0].max)
end