Language: C++

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

namespace ABC098A
{
    class Program
    {
        static void Main(string[] args)
        {
            int a, b, c, d, e;

            var word = Console.ReadLine().Split(' ');
            a = int.Parse(word[0]);
            b = int.Parse(word[1]);
            c = a + b;
            d = a - b;
            e = a * b;
            if (c>d&&c>e)
            {
                Console.WriteLine(c);
            }
            else if(d>c&&d>e)
            {
                Console.WriteLine(d);
            }
            else if (e > c && e > d)
            {
                Console.WriteLine(e);
            }
            else if (c==d||c==e)
            {
                Console.WriteLine(c);
            }
            else if ( d == e)
            {
                Console.WriteLine(d);
            }
         
            Console.ReadKey();
        }
    }
}


Compiler output:
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.Linq;
      |       ^~~~~~
a.cc:4:7: error: expected nested-name-specifier before 'System'
    4 | using System.Text;
      |       ^~~~~~
a.cc:5:7: error: expected nested-name-specifier before 'System'
    5 | using System.Threading.Tasks;
      |       ^~~~~~
a.cc:11:26: error: 'string' has not been declared
   11 |         static void Main(string[] args)
      |                          ^~~~~~
a.cc:11:35: error: expected ',' or '...' before 'args'
   11 |         static void Main(string[] args)
      |                                   ^~~~
a.cc:44:6: error: expected ';' after class definition
   44 |     }
      |      ^
      |      ;
a.cc: In static member function 'static void ABC098A::Program::Main(int*)':
a.cc:15:13: error: 'var' was not declared in this scope
   15 |             var word = Console.ReadLine().Split(' ');
      |             ^~~
a.cc:16:17: error: expected primary-expression before 'int'
   16 |             a = int.Parse(word[0]);
      |                 ^~~
a.cc:17:17: error: expected primary-expression before 'int'
   17 |             b = int.Parse(word[1]);
      |                 ^~~
a.cc:23:17: error: 'Console' was not declared in this scope
   23 |                 Console.WriteLine(c);
      |                 ^~~~~~~
a.cc:27:17: error: 'Console' was not declared in this scope
   27 |                 Console.WriteLine(d);
      |                 ^~~~~~~
a.cc:31:17: error: 'Console' was not declared in this scope
   31 |                 Console.WriteLine(e);
      |                 ^~~~~~~
a.cc:35:17: error: 'Console' was not declared in this scope
   35 |                 Console.WriteLine(c);
      |                 ^~~~~~~
a.cc:39:17: error: 'Console' was not declared in this scope
   39 |                 Console.WriteLine(d);
      |                 ^~~~~~~
a.cc:42:13: error: 'Console' was not declared in this scope
   42 |             Console.ReadKey();
      |             ^~~~~~~