Language: C++

using System;
using System.Linq;

namespace AOJ_console
{
    class _1_5_A
    {
        static void Main()
        {
            var rect = Console.ReadLine().Split(' ').Select(x => int.Parse(x)).ToList();
            Enumerable.Range(1, rect[0]).Select(x => Enumerable.Range(1, rect[1]).Aggregate("", (str, y) => str += "#").Trim()).ToList().ForEach(x => Console.WriteLine(x));
        }
    }
}

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.Linq;
      |       ^~~~~~
a.cc:13:6: error: expected ';' after class definition
   13 |     }
      |      ^
      |      ;
a.cc: In static member function 'static void AOJ_console::_1_5_A::Main()':
a.cc:10:13: error: 'var' was not declared in this scope
   10 |             var rect = Console.ReadLine().Split(' ').Select(x => int.Parse(x)).ToList();
      |             ^~~
a.cc:11:13: error: 'Enumerable' was not declared in this scope
   11 |             Enumerable.Range(1, rect[0]).Select(x => Enumerable.Range(1, rect[1]).Aggregate("", (str, y) => str += "#").Trim()).ToList().ForEach(x => Console.WriteLine(x));
      |             ^~~~~~~~~~
a.cc:11:33: error: 'rect' was not declared in this scope
   11 |             Enumerable.Range(1, rect[0]).Select(x => Enumerable.Range(1, rect[1]).Aggregate("", (str, y) => str += "#").Trim()).ToList().ForEach(x => Console.WriteLine(x));
      |                                 ^~~~
a.cc:11:49: error: 'x' was not declared in this scope
   11 |             Enumerable.Range(1, rect[0]).Select(x => Enumerable.Range(1, rect[1]).Aggregate("", (str, y) => str += "#").Trim()).ToList().ForEach(x => Console.WriteLine(x));
      |                                                 ^
a.cc:11:52: error: expected primary-expression before '>' token
   11 |             Enumerable.Range(1, rect[0]).Select(x => Enumerable.Range(1, rect[1]).Aggregate("", (str, y) => str += "#").Trim()).ToList().ForEach(x => Console.WriteLine(x));
      |                                                    ^
a.cc:11:98: error: 'str' was not declared in this scope; did you mean 'std'?
   11 |             Enumerable.Range(1, rect[0]).Select(x => Enumerable.Range(1, rect[1]).Aggregate("", (str, y) => str += "#").Trim()).ToList().ForEach(x => Console.WriteLine(x));
      |                                                                                                  ^~~
      |                                                                                                  std
a.cc:11:103: error: 'y' was not declared in this scope
   11 |             Enumerable.Range(1, rect[0]).Select(x => Enumerable.Range(1, rect[1]).Aggregate("", (str, y) => str += "#").Trim()).ToList().ForEach(x => Console.WriteLine(x));
      |                                                                                                       ^
a.cc:11:107: error: expected primary-expression before '>' token
   11 |             Enumerable.Range(1, rect[0]).Select(x => Enumerable.Range(1, rect[1]).Aggregate("", (str, y) => str += "#").Trim()).ToList().ForEach(x => Console.WriteLine(x));
      |                                                                                                           ^
a.cc:11:149: error: expected primary-expression before '>' token
   11 |             Enumerable.Range(1, rect[0]).Select(x => Enumerable.Range(1, rect[1]).Aggregate("", (str, y) => str += "#").Trim()).ToList().ForEach(x => Console.WriteLine(x));
      |                                                                                                                                                     ^
a.cc:11:151: error: 'Console' was not declared in this scope
   11 |             Enumerable.Range(1, rect[0]).Select(x => Enumerable.Range(1, rect[1]).Aggregate("", (str, y) => str += "#").Trim()).ToList().ForEach(x => Console.WriteLine(x));
      |                                                                                                                                                       ^~~~~~~