Problem:
Score : 300 points

Problem Statement

Compute A \times B, truncate its fractional part, and print the result as an integer.

Constraints

0 \leq A \leq 10^{15}

0 \leq B < 10

A is an integer.

B is a number with two digits after the decimal point.

Input

Input is given from Standard Input in the following format:

A B

Output

Print the answer as an integer.

Sample Input 1

198 1.10

Sample Output 1

217

We have 198 \times 1.10 = 217.8. After truncating the fractional part, we have the answer: 217.

Sample Input 2

1 0.01

Sample Output 2

0

Sample Input 3

1000000000000000 9.99

Sample Output 3

9990000000000000

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

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ABC169
{
    class Program
    {
        static void Main(string[] args)
        {
            //b();
            //c();
            //d();
            cc();
        }

        public static void b()
        {
            long n = long.Parse(Console.ReadLine());
            long[] a = Console.ReadLine().Split(' ').Select(long.Parse).ToArray();
            long b = 1000000000000000000;
            long ans = 1;
            bool flg = true;
            foreach (var x in a)
            {
                ans *= x;
                if(ans == 0)
                {
                    Console.WriteLine(0);
                    return;
                }
                else if(ans < 0)
                {
                    flg = false;
                }
            }
            if (ans > b)
            {
                Console.WriteLine(-1);
            }
            else if (flg == false)
            {
                Console.WriteLine(-1);
            }
            else
            {
                Console.WriteLine(ans);
            }
        }

        public static void c()
        {
            double[] ab = Console.ReadLine().Split(' ').Select(double.Parse).ToArray();
            double a = ab[0], b = ab[1] * 100;
            long ans =  (long)(a * b) / 100;
            Console.WriteLine(ans);
        }

        public static void d()
        {
            long n = long.Parse(Console.ReadLine());
            if(n == 1)
            {
                Console.WriteLine(0);
                return;
            }
            int ans = 0;
            int i = 2;
            bool flg = true;
            while(flg)
            {
                if(n == 1 || n < i)
                {
                    flg = false;
                }
                if(n % i == 0)
                {
                    n /= i;
                    if(n == 1 || n < i)
                    {
                        flg = false;
                    }
                }
                else
                {
                    i++;
                    continue;
                }
                i++;
                ans++;
            }
            Console.WriteLine(ans);
        }

        public static void cc()
        {
            string[] ab = Console.ReadLine().Split(' ');
            long a = long.Parse(ab[0]);
            double b = double.Parse(ab[1]);
            Console.WriteLine(Math.Floor(a * b));
        }
    }
}