import java.util.*;

class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long A = sc.nextLong();
		String B = sc.next();
		sc.close();
		String[] bs_str = B.split("\\.");
		long ans = (A * Integer.parseInt(bs_str[0]+bs_str[1]))/100;
		System.out.println(ans);
	}
} import java.util.*; util.* java class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long A = sc.nextLong();
		String B = sc.next();
		sc.close();
		String[] bs_str = B.split("\\.");
		long ans = (A * Integer.parseInt(bs_str[0]+bs_str[1]))/100;
		System.out.println(ans);
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long A = sc.nextLong();
		String B = sc.next();
		sc.close();
		String[] bs_str = B.split("\\.");
		long ans = (A * Integer.parseInt(bs_str[0]+bs_str[1]))/100;
		System.out.println(ans);
	} main {
		Scanner sc = new Scanner(System.in);
		long A = sc.nextLong();
		String B = sc.next();
		sc.close();
		String[] bs_str = B.split("\\.");
		long ans = (A * Integer.parseInt(bs_str[0]+bs_str[1]))/100;
		System.out.println(ans);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) long A = sc.nextLong(); A sc.nextLong() sc.nextLong sc String B = sc.next(); B sc.next() sc.next sc sc.close() sc.close sc String[] bs_str = B.split("\\."); bs_str B.split("\\.") B.split B "\\." long ans = (A * Integer.parseInt(bs_str[0]+bs_str[1]))/100; ans (A * Integer.parseInt(bs_str[0]+bs_str[1]))/100 (A * Integer.parseInt(bs_str[0]+bs_str[1])) A Integer.parseInt(bs_str[0]+bs_str[1]) Integer.parseInt Integer bs_str[0]+bs_str[1] bs_str[0] bs_str 0 bs_str[1] bs_str 1 100 System.out.println(ans) System.out.println System.out System System.out ans String[] args args
import java.util.*;

class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long A = sc.nextLong();
		String B = sc.next();
		sc.close();
		String[] bs_str = B.split("\\.");
		long ans = (A * Integer.parseInt(bs_str[0]+bs_str[1]))/100;
		System.out.println(ans);
	}
}
