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

public class Main {

  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    long a = sc.nextLong();
    String b = sc.next();

    char[] c = b.toCharArray();

    // for (int i = 0; i < 4; i++) {
    //   System.out.println(c[i]);
    // }

    long k = (c[0]-'0')*100+(c[2]-'0')*10+(c[3]-'0');

    long ans = a*k/100;

    System.out.println(ans);
  }

}

/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