import java.util.*;
import java.math.*;
 
public class Main {
    public static void main(String[] args) throws Exception {
        
        Scanner sc = new Scanner(System.in);
         
        long A = sc.nextLong();
      
      	double B = sc.nextDouble();
      		
      	BigDecimal bd_A = new BigDecimal(A);
      	BigDecimal bd_B = new BigDecimal(String.valueOf(B));
	
      	BigDecimal bd_C = bd_A.multiply(bd_B);
       
      	long l = bd_C.longValue();

      	System.out.println(l);
      

    }
}
/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