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;
using System.Collections.Generic;
using System.Linq;

namespace AtCoderContest
{
    class Program
    {
        static void Main()
        {
            var n = int.Parse(Console.ReadLine());
            var aArray = new List<decimal>();
            for(var i = 0; i < n; i++)
            {
                var str = Console.ReadLine();
                if (str.IndexOf('.') != -1)
                {
                    var decimalPart = str.Split('.')[1];
                    if (decimalPart.ToList().FindLastIndex(c => c != '0') > 4)
                    {
                        continue;
                    }
                }
                aArray.Add(decimal.Parse(str));
            }

            var count = 0;
            for (var i = 0; i < aArray.Count() - 1; i++)
            {
                for (var j = i + 1; j < aArray.Count(); j++)
                {
                    var product = aArray[i] * aArray[j];
                    count += (product == (int)product) ? 1 : 0;
                }
            }

            Console.WriteLine(count);
        }
    }
}