import sys

input = sys.stdin.readline



if __name__ == "__main__":

    a,b = input().split()

    ai = int(a)

    bf = round(float(b)*100)

    print((ai*bf//100))

import sys

input = sys.stdin.readline



if __name__ == "__main__":

    a,b = input().split()

    print((int(a) * round(float(b)*100)//100))

import sys

input = sys.stdin.readline
if __name__ == "__main__":
    a, b = input().split()
    ai = int(a)
    bf = round(float(b) * 100)
    print((ai * bf // 100))

import sys

input = sys.stdin.readline
if __name__ == "__main__":
    a, b = input().split()
    print((int(a) * round(float(b) * 100) // 100))

-    ai = int(a) -    bf = round(float(b) * 100) -    print((ai * bf // 100)) +    print((int(a) * round(float(b) * 100) // 100))