// Slower C++ solution:
#include<bits/stdc++.h>

#include <ext/pb_ds/assoc_container.hpp>

#include <ext/pb_ds/tree_policy.hpp>

using namespace __gnu_pbds;

using namespace std;

using ll=long long;

using db=double;



///***************************************************** CONSTANTS ******************************************************///



int const N=1e6+3;

ll MOD=1e9+7,fact[N];

const long long inf=(long long)1e18;

const long double PI=3.14159265358979;



///************************************************ CONTAINER DEFINITIONS ***********************************************///



typedef vector<int> vi;

typedef vector<ll> vl;

typedef pair<int,int> pii;

typedef pair<ll, ll> pll;

typedef vector<pii> vii;

typedef vector<pll> vll;

typedef set<int> si;

typedef set<ll> sl;

typedef map<int,int> mii;

typedef map<ll,ll> mll;



///************************************************ SHORT FORM KEYWORDS *************************************************///



#define PB push_back

#define F first

#define S second

#define MP make_pair

#define I insert

#define lb lower_bound

#define ub upper_bound

#define endl '\n'



///************************************************ SHORT FORM FUNCTIONS ************************************************///



#define loop(i,a,b) for(ll i=a;i<b;i++)

#define loopr(i,a,b) for(ll i=a-1;i>=b;i--)

#define afor(x, y) for (auto x : y)

#define mem(a,b) memset(a, b, sizeof(a) )

#define gcd(a,b) __gcd(a,b)

#define lcm(a,b) (a*(b/gcd(a,b)))

#define sa(v) sort(v.begin(),v.end())

#define sd(v) sort(v.begin(),v.end(),greater<>())

#define rev(s) reverse(s.begin(),s.end())

#define stll(x) stoll(x, nullptr, 10);

#define yes cout<<"YES"<<endl;

#define no cout<<"NO"<<endl;

#define mx(a) *max_element(all(a))

#define mn(a) *min_element(all(a))

#define all(a) a.begin(),a.end()

#define mxa(a,N) *max_element(a,a+N)

#define mna(a,N) *min_element(a,a+N)

#define print(a) {for(auto x:a)cout<<x<<" ";cout<<endl;}



///******************************************** FAST IO $ FILE INPUT ****************************************************///



#define io() ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);

#define fraction() cout.unsetf(ios::floatfield); cout.precision(10); cout.setf(ios::fixed,ios::floatfield);

#define fio() freopen("input_file_name","r",stdin);freopen("output_file_name","w",stdout);



///********************************************* REQUIRED FUNCTIONS *****************************************************///



ll powmod(ll a,ll b){ll p=MOD;a%=p;if(!a) return 0;ll pr=1;while(b>0){if(b&1){pr*=a;pr%=p;--b;}a*=a;a%=p;b/=2;}return pr;}

ll inv(ll a,ll p){return powmod(a,p-2);}

ll nCr(ll n,ll k,ll p){fact[0]=1;loop(i,1,n+1) fact[i]=fact[i-1]*i;return ((fact[n]*inv(fact[k],p)%p)*inv(fact[n-k],p))%p;}

bool isPrime(ll n){ if(n<=1)return false;if(n<=3)return true;if(n%2==0 or n%3==0)return false;for(ll i=5;i*i<=n;i+=6){if(n%i==0|n%(i+2)==0)return false;}return true;}



///######################################################################################################################///



typedef tree<pair<ll,ll>, null_type, less<pair<ll,ll>>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;



///************************************************ SOLUTION STARTS HERE ************************************************///

///======================================================================================================================///





void solve()

{

    long double a,b;

    cin>>a>>b;

    b*=1000;

    a*=b;

    a/=1000;

    //ll m=a;

    cout<<(ll) a<<endl;

}



int main()

{

    io();

    int $=1;//cin>>$;

    while($--) solve();

    return 0;

}






















// Faster C++ solution for the same problem (measured speedup: 4.839359221455898x):
#include<stdio.h>

#include<math.h>

int main()

{

	long long int a,b,ans;

    double s;

	scanf("%lld %lf",&a,&s);

	b=round(s*100);

	ans=a*b/100;

	printf("%lld",ans);

}