Language: C++

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

namespace P0003_Is_it_a_Right_Triangle
{
    class Program
    {
        static void Main(string[] args)
        {

            List<string> lines = new List<string>();

            int cntLine = int.Parse(Console.ReadLine());

            for(int i = 1; i <= cntLine; i++)
            {
                lines.Add(Console.ReadLine());
            }          

            foreach (string line in lines)
            {
                List<string> sidesStr = line.Split(' ').ToList<string>();
                List<int> sides = new List<int>();

                foreach (string sideStr in sidesStr)
                {
                    sides.Add(int.Parse(sideStr));
                }

                sides.Sort();

                if (Math.Pow(sides[2], 2) == Math.Pow(sides[0], 2) + Math.Pow(sides[1], 2))
                {
                    Console.WriteLine("YES");
                }
                else
                {
                    Console.WriteLine("NO");
                }

            }


        }
    }
}

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:10:26: error: 'string' has not been declared
   10 |         static void Main(string[] args)
      |                          ^~~~~~
a.cc:10:35: error: expected ',' or '...' before 'args'
   10 |         static void Main(string[] args)
      |                                   ^~~~
a.cc:47:6: error: expected ';' after class definition
   47 |     }
      |      ^
      |      ;
a.cc: In static member function 'static void P0003_Is_it_a_Right_Triangle::Program::Main(int*)':
a.cc:13:13: error: 'List' was not declared in this scope
   13 |             List<string> lines = new List<string>();
      |             ^~~~
a.cc:13:18: error: 'string' was not declared in this scope
   13 |             List<string> lines = new List<string>();
      |                  ^~~~~~
a.cc:13:26: error: 'lines' was not declared in this scope
   13 |             List<string> lines = new List<string>();
      |                          ^~~~~
a.cc:13:38: error: 'List' does not name a type
   13 |             List<string> lines = new List<string>();
      |                                      ^~~~
a.cc:13:51: error: expected primary-expression before ')' token
   13 |             List<string> lines = new List<string>();
      |                                                   ^
a.cc:15:27: error: expected primary-expression before 'int'
   15 |             int cntLine = int.Parse(Console.ReadLine());
      |                           ^~~
a.cc:19:27: error: 'Console' was not declared in this scope
   19 |                 lines.Add(Console.ReadLine());
      |                           ^~~~~~~
a.cc:22:29: error: expected ')' before 'line'
   22 |             foreach (string line in lines)
      |                             ^~~~
a.cc:22:21: note: to match this '('
   22 |             foreach (string line in lines)
      |                     ^
a.cc:22:13: error: 'foreach' was not declared in this scope
   22 |             foreach (string line in lines)
      |             ^~~~~~~