import java.util.*;
import java.io.*;
import static java.lang.Math.*;

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();
		String B = b.replace(".", "");
		
		// 計算
		long result = 0;
		result = (a*Long.valueOf(B))/100;
		
		// 出力
		System.out.println(result);
	}

} import java.util.*; util.* java import java.io.*; io.* java import static java.lang.Math.*; import static java.lang.Math.*; import static java.lang.Math.*; 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();
		String B = b.replace(".", "");
		
		// 計算
		long result = 0;
		result = (a*Long.valueOf(B))/100;
		
		// 出力
		System.out.println(result);
	}

} 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();
		String B = b.replace(".", "");
		
		// 計算
		long result = 0;
		result = (a*Long.valueOf(B))/100;
		
		// 出力
		System.out.println(result);
	} main {
		Scanner sc = new Scanner(System.in);
		
		// 入力
		long a = sc.nextLong();
		String b = sc.next();
		String B = b.replace(".", "");
		
		// 計算
		long result = 0;
		result = (a*Long.valueOf(B))/100;
		
		// 出力
		System.out.println(result);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) long a = sc.nextLong(); a sc.nextLong() sc.nextLong sc String b = sc.next(); b sc.next() sc.next sc String B = b.replace(".", ""); B b.replace(".", "") b.replace b "." "" long result = 0; result 0 result = (a*Long.valueOf(B))/100 result (a*Long.valueOf(B))/100 (a*Long.valueOf(B)) a Long.valueOf(B) Long.valueOf Long B 100 System.out.println(result) System.out.println System.out System System.out result String[] args args 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();
		String B = b.replace(".", "");
		
		// 計算
		long result = 0;
		result = (a*Long.valueOf(B))/100;
		
		// 出力
		System.out.println(result);
	}

} 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();
		String B = b.replace(".", "");
		
		// 計算
		long result = 0;
		result = (a*Long.valueOf(B))/100;
		
		// 出力
		System.out.println(result);
	}

} Main
import java.util.*;
import java.io.*;
import static java.lang.Math.*;

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();
		String B = b.replace(".", "");
		
		// 計算
		long result = 0;
		result = (a*Long.valueOf(B))/100;
		
		// 出力
		System.out.println(result);
	}

}
