import java.util.*; 
import java.lang.*; 


public class Main{
	public static void main(String[] args){
		Scanner scan = new Scanner(System.in);
                
                long A = scan.nextLong();
                double B = scan.nextDouble()+0.001;
                long x = (long)B;
                double B1 = (B-x)*10;
                long y = (long)B1;
                double B2 = (B1-y)*10;
                long z = (long)B2;

                long ans1 = (A*(100*x+10*y+z))/100;
                System.out.println(ans1);
        }
}
/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