import java.math.BigDecimal;
import java.math.RoundingMode;
import java.util.*;
public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner sc = new Scanner(System.in);
		long a = sc.nextLong();
		double b = sc.nextDouble();
		
		BigDecimal bd = new BigDecimal(String.valueOf(a));
		BigDecimal bd1 = new BigDecimal(String.valueOf(b));
		BigDecimal bd2 = bd1.multiply(bd);
		BigDecimal bd3 = bd2.setScale(0, RoundingMode.DOWN);
		
		System.out.println(bd3);
	}

}
/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