import java.util.*;
import java.io.*;
import static java.lang.Math.*;
import java.math.BigInteger;
import java.math.BigDecimal;

public class Main {
    public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		
		// 入力
		long a = sc.nextLong();
		String b = sc.next();
		BigDecimal A = new BigDecimal(a);
		BigDecimal B = new BigDecimal(b);
		
		// 計算
		
		// 出力
		System.out.println(A.multiply(B).toBigInteger());
	}

}

/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