#!python3



iim = lambda: list(map(int, input().rstrip().split()))



def resolve():

    a, b = input().split()

    a = int(a); b = int(b.replace(".", ""))



    print((a*b//100))



if __name__ == "__main__":

    resolve()

#!python3



import sys



def resolve():

    a, b = sys.stdin.read().split()

    a = int(a); b = int(b.replace(".", ""))



    print((a*b//100))



if __name__ == "__main__":

    resolve()

#!python3
iim = lambda: list(map(int, input().rstrip().split()))


def resolve():
    a, b = input().split()
    a = int(a)
    b = int(b.replace(".", ""))
    print((a * b // 100))


if __name__ == "__main__":
    resolve()

#!python3
import sys


def resolve():
    a, b = sys.stdin.read().split()
    a = int(a)
    b = int(b.replace(".", ""))
    print((a * b // 100))


if __name__ == "__main__":
    resolve()

-iim = lambda: list(map(int, input().rstrip().split())) +import sys -    a, b = input().split() +    a, b = sys.stdin.read().split()