using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Text;
using System.Text.RegularExpressions;
using System.Linq;


class Magatro
{
    static void Main()
    {
        string[] s = Console.ReadLine().Split(' ');
        string[] w = s[0].Split('.');
        int v = int.Parse(w[1]);
        int t = int.Parse(s[1]);
        Console.WriteLine(v * t / 10000);
    }
}