#include <iostream>
#include <math.h>
#include <algorithm>
using namespace std;
typedef long long ll;
int main(void){
    ll a,b;
    long double c;
    ll ans = 0;
    cin >> a >> c;
    b = c*100;
    ans = a * b;
    ans /= 100;
    cout << ans << endl;
    return 0;
}
