Problem:
Score : 300 points

Problem Statement

You are given N real values A_1, A_2, \ldots, A_N.
Compute the number of pairs of indices (i, j)
such that i < j and the product A_i \cdot A_j is integer.

Constraints

2 \leq N \leq 200\,000

0 < A_i < 10^4

A_i is given with at most 9 digits after the decimal.

Input

Input is given from Standard Input in the following format.

N
A_1
A_2
\vdots
A_N

Output

Print the number of pairs with integer product A_i \cdot A_j (and i < j).

Sample Input 1

5
7.5
2.4
17.000000001
17
16.000000000

Sample Output 1

3

There are 3 pairs with integer product:

7.5 \cdot 2.4 = 18

7.5 \cdot 16 = 120

17 \cdot 16 = 272

Sample Input 2

11
0.9
1
1
1.25
2.30000
5
70
0.000000001
9999.999999999
0.999999999
1.000000001

Sample Output 2

8

Solution in C# (.NET Core 3.1.201) (judge verdict: Wrong Answer)

using System;

namespace ConsoleApp7
{
    class Program
    {
        static void Main(string[] args)
        {
            int a2 = int.Parse(Console.ReadLine());
            double[] c1 = new double[a2];
            for (int i = 0; i < a2; i++)
            {
                c1[i] = double.Parse(Console.ReadLine());
            }
            for (int i = 0; i < a2; i++)
            {
                if (c1[i] * 10000 % 1 != 0)
                {
                    c1[i] = 0;
                }
            }
            int cnt = 0;
            for (int i = 0; i < a2 - 1; i++)
            {
                if (c1[i] != 0)
                {
                    for (int j = i + 1; j < a2; j++)
                    {
                        if (c1[j] != 0)
                        {
                            if (c1[i] * c1[j] % 1 == 0)
                            {
                                cnt++;
                            }
                        }
                    }
            }
        }
            Console.WriteLine(cnt);
            //Console.ReadLine();
        }
    }
}