import java.io.*;
import java.util.*;

public class Main {

    public static void main(String[] args) throws IOException {
        long a = in.nextLong();
        long b = Math.round(in.nextDouble() * 100);
      
        /*
            Directly multiply float and int could result in precision errors.
            First convert float to int and calculate the result. Then if needed it could
            be converted back to float.
            All multiply float by 100 could not work as expected. for example,
            9.79 * 100 = 978. To handle such cases use Math.round which rounds the value to 
            nearest integer.
        */
        
        long ans = (a * b) / 100;
        println(ans); 
        in.close();
        out.close();
    }

    static int MIN = Integer.MIN_VALUE;
    static int MAX = Integer.MAX_VALUE;
    static Reader in = new Reader();
    static PrintWriter out = new PrintWriter(System.out);

    static int[] readInt(int N) throws IOException { 
    	int arr[] = new int[N];
    	for(int i = 0; i < N; i++){ 
    		arr[i] = in.nextInt(); 
    	} 
    	return arr;
    }
    
    static long[] readLong(int N) throws IOException { 
    	long arr[] = new long[N];
    	for(int i = 0; i < N; i++){ 
    		arr[i] = in.nextLong(); 
    	} 
    	return arr;
    }
    
    static String[] readString(int N) throws IOException { 
    	String arr[] = new String[N];
    	for(int i = 0; i < N; i++){ 
    		arr[i] = in.next(); 
    	} 
    	return arr;
    }
    
    static void print(Object O) {  
    	out.print(O); 
    }
    
    static void println(Object O) { 
    	out.println(O); 
    }
    
    static void println(int arr[]) { 
    	for(int i = 0; i < arr.length; i++){ 
    		print(arr[i] + " "); 
    	} 
    	println(""); 
    }
    
    static void debug(Object ... O) { 
    	for(Object obj: O){
    		System.out.print(obj + " ");
    	}
    	System.out.println();
    }
}

class Reader {
    BufferedReader reader;
    StringTokenizer tokenizer;

    Reader() {
        reader = new BufferedReader(new InputStreamReader(System.in));
        tokenizer = new StringTokenizer("");
    }

    String next() throws IOException {
        while (!tokenizer.hasMoreTokens() ) { 
            tokenizer = new StringTokenizer(reader.readLine()); 
        }
        return tokenizer.nextToken();
    }

    int nextInt() throws IOException { 
        return Integer.parseInt(next()); 
    }
    
    double nextDouble() throws IOException { 
        return Double.parseDouble(next());
    }
    
    long nextLong() throws IOException { 
        return Long.parseLong(next()); 
    }
    
    String nextLine() throws IOException { 
        return reader.readLine(); 
    }
    
    void close() throws IOException { 
        reader.close(); 
    }
}
/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