import Foundation
func toTuple<T>(_ args: [T]) -> (T, T) { (args[0], args[1]) }
func toTuple<T>(_ args: [T]) -> (T, T, T) { (args[0], args[1], args[2]) }
func toTuple<T>(_ args: [T]) -> (T, T, T, T) { (args[0], args[1], args[2], args[3]) }
func readInts() -> [Int] { readLine()!.split(separator: " ").map { Int($0)! } }
func readDoubles() -> [Double] { readLine()!.split(separator: " ").map { Double($0)! } }
func readStrings() -> [String] { readLine()!.split(separator: " ").map { String($0) } }

let (A, B) = toTuple(readStrings())
let a = Int(A)!
let bSplit = B.split(separator: ".")
let b = Int(String(bSplit[0]+bSplit[1]))!
print(a * b / 100)