#include<iostream>
#include<algorithm>
#include<string>
using namespace std;
int main(){
	long long int A,B;
	string b;
	cin>>A>>b;
	if(b[1]=='.')B=(b[0]-'0')*100+(b[2]-'0')*10+(b[3]-'0');
	else B=(b[0]-'0')*1000+(b[1]-'0')*100+(b[3]-'0')*10+(b[4]-'0');
	cout<<A*B/100;
	return 0;
}