Language: C++

using System;
using System.Collections.Generic;
using System.Text;
using System.Threading.Tasks;

namespace test
{
   class Program
   {
      static void Main(string[] args)
      {
        Console.Write(r * r * ?? + " " + 2 * r * ??);

Compiler output:
a.cc:12:50: warning: trigraph ??) ignored, use -trigraphs to enable [-Wtrigraphs]
   12 |         Console.Write(r * r * ?? + " " + 2 * r * ??);
a.cc:1:7: error: expected nested-name-specifier before 'System'
    1 | using System;
      |       ^~~~~~
a.cc:2:7: error: expected nested-name-specifier before 'System'
    2 | using System.Collections.Generic;
      |       ^~~~~~
a.cc:3:7: error: expected nested-name-specifier before 'System'
    3 | using System.Text;
      |       ^~~~~~
a.cc:4:7: error: expected nested-name-specifier before 'System'
    4 | using System.Threading.Tasks;
      |       ^~~~~~
a.cc:10:24: error: 'string' has not been declared
   10 |       static void Main(string[] args)
      |                        ^~~~~~
a.cc:10:33: error: expected ',' or '...' before 'args'
   10 |       static void Main(string[] args)
      |                                 ^~~~
a.cc:12:54: error: expected '}' at end of input
   12 |         Console.Write(r * r * ?? + " " + 2 * r * ??);
      |                                                      ^
a.cc:9:4: note: to match this '{'
    9 |    {
      |    ^
a.cc: In static member function 'static void test::Program::Main(int*)':
a.cc:12:9: error: 'Console' was not declared in this scope
   12 |         Console.Write(r * r * ?? + " " + 2 * r * ??);
      |         ^~~~~~~
a.cc:12:23: error: 'r' was not declared in this scope
   12 |         Console.Write(r * r * ?? + " " + 2 * r * ??);
      |                       ^
a.cc:12:31: error: expected primary-expression before '?' token
   12 |         Console.Write(r * r * ?? + " " + 2 * r * ??);
      |                               ^
a.cc:12:32: error: expected primary-expression before '?' token
   12 |         Console.Write(r * r * ?? + " " + 2 * r * ??);
      |                                ^
a.cc:12:50: error: expected primary-expression before '?' token
   12 |         Console.Write(r * r * ?? + " " + 2 * r * ??);
      |                                                  ^
a.cc:12:51: error: expected primary-expression before '?' token
   12 |         Console.Write(r * r * ?? + " " + 2 * r * ??);
      |                                                   ^
a.cc:12:52: error: expected primary-expression before ')' token
   12 |         Console.Write(r * r * ?? + " " + 2 * r * ??);
      |                                                    ^
a.cc:12:52: error: expected ':' before ')' token
a.cc:12:52: error: expected primary-expression before ')' token
a.cc:12:52: error: expected ':' before ')' token
a.cc:12:52: error: expected primary-expression before ')' token
a.cc:12:52: error: expected ':' before ')' token
a.cc:12:52: error: expected primary-expression before ')' token
a.cc:12:52: error: expected ':' before ')' token
a.cc:12:52: error: expected primary-expression before ')' token
a.cc:12:54: error: expected '}' at end of input
   12 |         Console.Write(r * r * ?? + " " + 2 * r * ??);
      |                                                      ^
a.cc:11:7: note: to match this '{'
   11 |       {
      |       ^
a.cc: At global scope:
a.cc:12:54: error: expected unqualified-id at end of input
   12 |         Console.Write(r * r * ?? + " " + 2 * r * ??);
      |                                                      ^
a.cc:12:54: error: expected '}' at end of input
a.cc:7:1: note: to match this '{'
    7 | {
      | ^