defmodule Main do
  def main do
    [a,b]=IO.gets("") |> String.trim |> String.split(" ")
    x=String.to_integer(a)
    y=String.replace(b,".","")
    |>String.to_integer
    x*y
    |> Integer.to_string
    |> String.slice(0..-3)
    |> (fn x->if x=="" do
    IO.puts("0")
    else
    IO.puts(x)
    end
    end).()
  end
end
