import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Scanner;

public class Main{
	public static void main(String args[]) {
		Scanner sc = new Scanner(System.in);
		BigInteger myBI = new BigInteger(sc.next());
		double a = sc.nextDouble();
		BigDecimal bd = new BigDecimal(myBI);
		BigInteger doubleWithStringValue = bd.multiply(BigDecimal.valueOf(a)).toBigInteger();
		long result=doubleWithStringValue.longValue();
		System.out.println(result);
	}
}

/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz