import java.util.*;
import java.lang.Math.*;
import java.math.BigDecimal;
public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		// スペース区切りの整数の入力
		long syaink = sc.nextLong();
        BigDecimal ss = BigDecimal.valueOf(syaink);
        double syainj = sc.nextDouble();
        BigDecimal ssc =BigDecimal.valueOf(syainj);
      BigDecimal b3 = ss.multiply(ssc);
      BigDecimal result3 = b3.setScale(0, BigDecimal.ROUND_DOWN);
      System.out.println(result3);
}
}
/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