import Foundation

private func readInt() -> [Int]{
    return readLine()!.split(separator: " ").map{Int($0)!}
}

func mainC() {
    let line = readLine()!.split(separator: " ")
    let a = Int(line[0])!
    let b = Double(line[1])! * 100
    let ans = a * Int(b)
    print(ans / 100)
}

mainC()
