import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long a = sc.nextLong();
		double b = sc.nextDouble();
		long ib = (long) (b * 100 + 0.5);
		a *= ib;
		a /= 100;
		System.out.println(a);
		
		sc.close();
	}
}

 import java.util.Scanner; Scanner java.util public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long a = sc.nextLong();
		double b = sc.nextDouble();
		long ib = (long) (b * 100 + 0.5);
		a *= ib;
		a /= 100;
		System.out.println(a);
		
		sc.close();
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long a = sc.nextLong();
		double b = sc.nextDouble();
		long ib = (long) (b * 100 + 0.5);
		a *= ib;
		a /= 100;
		System.out.println(a);
		
		sc.close();
	} main {
		Scanner sc = new Scanner(System.in);
		long a = sc.nextLong();
		double b = sc.nextDouble();
		long ib = (long) (b * 100 + 0.5);
		a *= ib;
		a /= 100;
		System.out.println(a);
		
		sc.close();
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) long a = sc.nextLong(); a sc.nextLong() sc.nextLong sc double b = sc.nextDouble(); b sc.nextDouble() sc.nextDouble sc long ib = (long) (b * 100 + 0.5); ib (long) (b * 100 + 0.5) b * 100 b 100 0.5 a *= ib a ib a /= 100 a 100 System.out.println(a) System.out.println System.out System System.out a sc.close() sc.close sc String[] args args public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long a = sc.nextLong();
		double b = sc.nextDouble();
		long ib = (long) (b * 100 + 0.5);
		a *= ib;
		a /= 100;
		System.out.println(a);
		
		sc.close();
	}
} public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long a = sc.nextLong();
		double b = sc.nextDouble();
		long ib = (long) (b * 100 + 0.5);
		a *= ib;
		a /= 100;
		System.out.println(a);
		
		sc.close();
	}
} Main
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long a = sc.nextLong();
		double b = sc.nextDouble();
		long ib = (long) (b * 100 + 0.5);
		a *= ib;
		a /= 100;
		System.out.println(a);
		
		sc.close();
	}
}


