a,b=input().split()
if b.count(".")==0:b+="."
b+="00000"
di=b.count(".")
B=""
for i in range(len(b)):
  if b[i]!=".":
    B+=b[i]
  if i==di+2:
    B+="."
b=int(B)
a=int(a)
print(a*b//100)


### FIXED CODE ###

# coding: utf-8
#import numpy as np
import re
import math
from collections import defaultdict
from collections import deque
import collections
from fractions import Fraction
from queue import PriorityQueue
import itertools
from copy import deepcopy
import random
from decimal import Decimal
import time
import os
import sys
import datetime
from functools import lru_cache
from functools import reduce
readline=sys.stdin.readline
sys.setrecursionlimit(2000000)
alphabet="abcdefghijklmnopqrstuvwxyz"
numbers="0123456789"
mod=int(10**9+7)
inf=int(10**19)
class Edge():
    def __init__(self,x,y,val=1):
        self.x=x
        self.y=y
        self.val=val
class unionfind():
    def __init__(self,n):
        self.n=n
        self.P=[a for a in range(n)]
        self.rank=[0]*n
 
    def find(self,x):
        if(x!=self.P[x]):
            self.P[x]=self.find(self.P[x])
        return self.P[x]
 
    def same(self,x,y):
        return self.find(x)==self.find(y)
 
    def link(self,x,y):
        if self.rank[x]<self.rank[y]:
            self.P[x]=y
        elif self.rank[y]<self.rank[x]:
            self.P[y]=x
        else:
            self.P[x]=y
            self.rank[y]+=1
 
    def unite(self,x,y):
        self.link(self.find(x),self.find(y))
 
    def size(self):
        S=set()
        for a in range(self.n):
            S.add(self.find(a))
        return len(S)
def yn(b):
    if b:print("yes")
    else:print("no")
def Yn(b):
    if b:print("Yes")
    else:print("No")
def YN(b):
    if b:print("YES")
    else:print("NO")
def ispow(a,b):
    now=b
    while now<a:
        now*=b
    return now==a
def getbin(num,size):
    A=[0]*size
    for a in range(size):
        if (num>>(size-a-1))&1==1:
            A[a]=1
        else:
            A[a]=0
    return A
def getfacs(n,mod_=0):
    A=[1]*(n+1)
    for a in range(2,len(A)):
        A[a]=A[a-1]*a
        if(mod_>0):A[a]%=mod_
    return A
def comb(n,r,mod,fac):
    if(n-r<0):return 0
    return (fac[n]*pow(fac[n-r],mod-2,mod)*pow(fac[r],mod-2,mod))%mod
def nextcomb(num,size):
    x=num&(-num)
    y=num+x
    z=num&(~y)
    z//=x
    z=z>>1
    num=(y|z)
    if(num>=(1<<size)):return False
    else:return num
def getprimes(n):
    if n==0:return []
    A=[True]*(n+1)
    A[0]=False
    A[1]=False
    for a in range(2,n+1):
        if A[a]:
            for b in range(a*2,n+1,a):
                A[b]=False
    ret=[]
    for a in range(n+1):
        if(A[a]):ret.append(a)
    return ret
def isprime(num):
    if(num<=1):return False
    i=2
    while i*i<=num:
       if(num%i==0):return False
       i+=1
    return True
def ifelse(bbool,ret1,ret2):
    if bbool:return ret1
    else:return  ret2
def join(A,c=" "):
    n=len(A)
    A=list(map(str,A))
    s=""
    for a in range(n):
        s+=A[a]
        if(a<n-1):s+=c
    return s
def factorize(n):
    b = 2
    ret=defaultdict(int)
    while b * b <= n:
        while n % b == 0:
            n //= b
            ret[b]+=1
        b+=1
    if n > 1:ret[n]+=1
    return ret
def pm(x):
    return x//abs(x)
def inputintlist(): 
    return list(map(int,input().split()))
def istanchouzouka(A):
    f=True
    prev=min(A)-1
    for a in A:
        if prev>=a:
            f=False
        prev=a
    return f
def istanchouhigensyou(A):
    f=True
    prev=min(A)-1
    for a in A:
        if prev>a:
            f=False
        prev=a
    return f
def getallsum(A):
    s=sum(A)
    dp=defaultdict(int)
    dp[0]=1
    for a in range(0,len(A)):
        for b in range(s,-1,-1):
            if b-A[a]>=0:
                dp[b]+=dp[b-A[a]]
    return dp
def yuukoutomukou(edges):
    ret=deepcopy(edges)
    for edge in edges:
        if not edge.x==edge.y:
            ret.append(Edge(edge.y,edge.x,edge.val))
    return ret
def dijkstra(edges,V,start):
    mincost=[inf]*V
    G=[[] for a in range(V)]
    for edge in edges:
        G[edge.x].append([edge.val,edge.y])
    Q=PriorityQueue()
    Q.put([0,start])#[cost,x]
    while not Q.empty():
        nowcost,nowx=Q.get()
        if mincost[nowx]==inf:
            mincost[nowx]=nowcost
            for cost,y in G[nowx]:
                newcost=nowcost+cost
                Q.put([newcost,y])
    return mincost
def warshallfloyd(edges,V):
    mincost=[[inf for b in range(V)] for a in range(V)]
    for a in range(V):mincost[a][a]=0
    for edge in edges:
        mincost[edge.x][edge.y]=min(mincost[edge.x][edge.y],edge.val)#x→yが複数ある場合のためにmin()する
    for k in range(V):
        for s in range(V):
            for t in range(V):
                if mincost[s][k]==inf or mincost[k][t]==inf:continue
                mincost[s][t]=min(mincost[s][t],mincost[s][k]+mincost[k][t])
    return mincost
def bellemanford(edges,V,start):
    mincost=[inf]*V
    mincost[start]=0
    for _ in range(V):
        for edge in edges:
            if mincost[edge.x]==inf:continue
            mincost[edge.y]=min(mincost[edge.y],mincost[edge.x]+edge.val)
    return mincost
def ruisekiwa(A):
    ret=[0]*(len(A)+1)
    for a in range(len(A)):
        ret[a+1]=ret[a]+A[a]
    return ret
def getmd(x1,y1,x2,y2):
    return abs(x1-x2)+abs(y1-y2)
def geted(x1,y1,x2,y2):
    return math.sqrt((x1-x2)**2+(y1-y2)**2)
class fordfulkerson():
    def __init__(self,edges,V,s,t):
        self.V=V
        self.used=[False]*V
        self.G=[[] for a in range(V)]
        self.s=s
        self.t=t
        for edge in edges:
            self.G[edge.x].append({"x":edge.x,"y":edge.y,"cap":edge.val,"rev":len(self.G[edge.y])})
            self.G[edge.y].append({"x":edge.y,"y":edge.x,"cap":0,"rev":len(self.G[edge.x])-1})
    def dfs(self,v,t,f=inf):
        if v==t:return f
        self.used[v]=True
        for a in range(len(self.G[v])):
            x=self.G[v][a]["x"]
            y=self.G[v][a]["y"]
            cap=self.G[v][a]["cap"]
            rev=self.G[y][self.G[x][a]["rev"]]
            if self.used[y] or cap==0:continue
            f2=self.dfs(y,t,min(f,cap))
            if f2>0:
                self.G[v][a]["cap"]-=f2
                rev["cap"]+=f2
                return f2
        return 0
    def maxflow(self):
        flow=0
        while True:
            self.used=[False]*V
            zouka=self.dfs(self.s,self.t)
            if zouka==0:break
            flow+=zouka
        return flow









######################################################################################################
A,B=input().split()
ans=Decimal(A)*Decimal(B)
ans=math.floor(ans)
print(ans)