Language: C++

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

namespace aoj4
{
    class Program
    {
        public void Solve()
        {
            String[] input = Console.ReadLine().Split(' ');
            int a = int.Parse(input[0]);
            int b = int.Parse(input[1]);
            if (a < b)
            {
                Console.WriteLine("a < b");
            }
            else if (a == b)
            {
                Console.WriteLine("a == b");
            }
            else
            {
                Console.WriteLine("a > b");
            }
        }

        static void Main(string[] args)
        {
            Program s = new Program();
            s.Solve();
        }
    }
}

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:11:15: error: expected ':' before 'void'
   11 |         public void Solve()
      |               ^~~~~
      |               :
a.cc:30:26: error: 'string' has not been declared
   30 |         static void Main(string[] args)
      |                          ^~~~~~
a.cc:30:35: error: expected ',' or '...' before 'args'
   30 |         static void Main(string[] args)
      |                                   ^~~~
a.cc:35:6: error: expected ';' after class definition
   35 |     }
      |      ^
      |      ;
a.cc: In member function 'void aoj4::Program::Solve()':
a.cc:13:13: error: 'String' was not declared in this scope
   13 |             String[] input = Console.ReadLine().Split(' ');
      |             ^~~~~~
a.cc:13:20: error: expected primary-expression before ']' token
   13 |             String[] input = Console.ReadLine().Split(' ');
      |                    ^
a.cc:14:21: error: expected primary-expression before 'int'
   14 |             int a = int.Parse(input[0]);
      |                     ^~~
a.cc:15:21: error: expected primary-expression before 'int'
   15 |             int b = int.Parse(input[1]);
      |                     ^~~
a.cc:18:17: error: 'Console' was not declared in this scope
   18 |                 Console.WriteLine("a < b");
      |                 ^~~~~~~
a.cc:22:17: error: 'Console' was not declared in this scope
   22 |                 Console.WriteLine("a == b");
      |                 ^~~~~~~
a.cc:26:17: error: 'Console' was not declared in this scope
   26 |                 Console.WriteLine("a > b");
      |                 ^~~~~~~
a.cc: In static member function 'static void aoj4::Program::Main(int*)':
a.cc:32:25: error: conversion from 'aoj4::Program*' to non-scalar type 'aoj4::Program' requested
   32 |             Program s = new Program();
      |                         ^~~~~~~~~~~~~