import Foundation

extension String {
    subscript(i: Int) -> Character {
        self[index(startIndex, offsetBy: i)]
    }
}

func inputInt() -> Int {
    Int(readLine()!)!
}

func inputDouble() -> Double {
    Double(readLine()!)!
}

func inputArray() -> [String] {
    readLine()!.components(separatedBy: " ")
}

func inputIntArray() -> [Int] {
    inputArray().map({ Int($0)! })
}

func inputDoubleArray() -> [Double] {
    inputArray().map({ Double($0)! })
}

let i = inputDoubleArray()
let a = Int(i[0])
let b = Int(i[1] * 100)
/*
let s = String(a * b)

print(String(s.prefix(s.count - 2)))
*/

print(a * b / 100)
