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++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

# include <bits/stdc++.h>

# define pb push_back
# define fr first
# define sc second
# define mk make_pair
# define int long long

using namespace std;

const int inf = 1e9 + 7;
const int N = 2002;

typedef long long ll;

int n, a[N], u[N], ans;

 main()
{
      cin >> n;

      for(int i = 1; i <= n; i ++)
            cin >> a[i];

      for(int i = n; i >= (n + 1) / 2; i --)
            if(a[i] < 0) u[i] = 1;

      for(int i = 1; i <= n; i ++)
      {
            int res = 0, bl = 1;
            for(int j = i; j <= n; j += i)
            {
                  res += a[j];
                  if(res > 0)
                  {
                        bl = 0;
                        break;
                  }
            }
            if(bl)
                  for(int j = i; j <= n; j += i)
                        u[j] = 1;
      }

      for(int i = 1; i <= n; i ++)
            if(!u[i]) ans += a[i];

      cout << ans << endl;
}