Language: C++

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

class B {
    public static void main(String args[]){
        FastReader sc=new FastReader(); 
        double a  = sc.nextDouble();
        double b  = sc.nextDouble();
        System.out.println((long)(a*b));
    }
       
    static class FastReader 
    { 
        BufferedReader br; 
        StringTokenizer st; 
  
        public FastReader() 
        { 
            br = new BufferedReader(new
                     InputStreamReader(System.in)); 
        } 
  
        String next() 
        { 
            while (st == null || !st.hasMoreElements()) 
            { 
                try
                { 
                    st = new StringTokenizer(br.readLine()); 
                } 
                catch (IOException  e) 
                { 
                } 
            } 
            return st.nextToken(); 
        } 
  
        int nextInt() 
        { 
            return Integer.parseInt(next()); 
        } 
  
        long nextLong() 
        { 
            return Long.parseLong(next()); 
        } 
  
        double nextDouble() 
        { 
            return Double.parseDouble(next()); 
        } 
  
        String nextLine() 
        { 
            String str = ""; 
            try
            { 
                str = br.readLine(); 
            } 
            catch (IOException e) 
            { 
                
            } 
            return str; 
        } 
    } 
}

Compiler output:
a.cc:1:1: error: 'import' does not name a type
    1 | import java.io.BufferedReader;
      | ^~~~~~
a.cc:1:1: note: C++20 'import' only available with '-fmodules-ts'
a.cc:2:1: error: 'import' does not name a type
    2 | import java.io.IOException;
      | ^~~~~~
a.cc:2:1: note: C++20 'import' only available with '-fmodules-ts'
a.cc:3:1: error: 'import' does not name a type
    3 | import java.io.InputStreamReader;
      | ^~~~~~
a.cc:3:1: note: C++20 'import' only available with '-fmodules-ts'
a.cc:4:1: error: 'import' does not name a type
    4 | import java.util.StringTokenizer;
      | ^~~~~~
a.cc:4:1: note: C++20 'import' only available with '-fmodules-ts'
a.cc:7:11: error: expected ':' before 'static'
    7 |     public static void main(String args[]){
      |           ^~~~~~~
      |           :
a.cc:7:29: error: 'String' has not been declared
    7 |     public static void main(String args[]){
      |                             ^~~~~~
a.cc:16:9: error: 'BufferedReader' does not name a type
   16 |         BufferedReader br;
      |         ^~~~~~~~~~~~~~
a.cc:17:9: error: 'StringTokenizer' does not name a type
   17 |         StringTokenizer st;
      |         ^~~~~~~~~~~~~~~
a.cc:19:15: error: expected ':' before 'FastReader'
   19 |         public FastReader()
      |               ^~~~~~~~~~~
      |               :
a.cc:25:9: error: 'String' does not name a type
   25 |         String next()
      |         ^~~~~~
a.cc:55:9: error: 'String' does not name a type
   55 |         String nextLine()
      |         ^~~~~~
a.cc:68:6: error: expected ';' after class definition
   68 |     }
      |      ^
      |      ;
a.cc:14:5: error: a storage class can only be specified for objects and functions
   14 |     static class FastReader
      |     ^~~~~~
a.cc:69:2: error: expected ';' after class definition
   69 | }
      |  ^
      |  ;
a.cc: In static member function 'static void B::main(int*)':
a.cc:8:23: error: conversion from 'B::FastReader*' to non-scalar type 'B::FastReader' requested
    8 |         FastReader sc=new FastReader();
      |                       ^~~~~~~~~~~~~~~~
a.cc:11:9: error: 'System' was not declared in this scope
   11 |         System.out.println((long)(a*b));
      |         ^~~~~~
a.cc: In constructor 'B::FastReader::FastReader()':
a.cc:21:13: error: 'br' was not declared in this scope
   21 |             br = new BufferedReader(new
      |             ^~
a.cc:21:22: error: expected type-specifier before 'BufferedReader'
   21 |             br = new BufferedReader(new
      |                      ^~~~~~~~~~~~~~
a.cc: In member function 'int B::FastReader::nextInt()':
a.cc:42:20: error: 'Integer' was not declared in this scope
   42 |             return Integer.parseInt(next());
      |                    ^~~~~~~
a.cc:42:37: error: 'next' was not declared in this scope; did you mean 'nextInt'?
   42 |             return Integer.parseInt(next());
      |                                     ^~~~
      |                                     nextInt
a.cc: In member function 'long int B::FastReader::nextLong()':
a.cc:47:20: error: 'Long' was not declared in this scope; did you mean 'long'?
   47 |             return Long.parseLong(next());
      |                    ^~~~
      |                    long
a.cc:47:35: error: 'next' was not declared in this scope; did you mean 'nextInt'?
   47 |             return Long.parseLong(next());
      |                                   ^~~~
      |                                   nextInt
a.cc: In member function 'double B::FastReader::nextDouble()':
a.cc:52:20: error: 'Double' was not declared in this scope; did you mean 'double'?
   52 |             return Double.parseDouble(next());
      |                    ^~~~~~
      |                    double
a.cc:52:39: error: 'next' was not declared in this scope; did you mean 'nextInt'?
   52 |             return Double.parseDouble(next());
      |                                       ^~~~
      |                                       nextInt