05. Special Numbers

using System;

namespace SpecialNumbers
{
    class Program
    {
        static void Main(string[] args)
        {
            string n = Console.ReadLine();

            for (int i = 1; i <= int.Parse(n); i++)
            {
                int sum = 0;
                int x = i;
                for (int j = 0; j < i.ToString().Length; j++)
                {
                    sum += x % 10;
                    x /= 10;
                }

                if (sum == 5 || sum == 7 || sum == 11)
                {
                    Console.WriteLine($"{i} -> True");
                }
                else
                {
                    Console.WriteLine($"{i} -> False");
                }
            }
        }
    }
}




Решение с LINQ:

using System;
using System.Linq;

namespace SpecialNumbers
{
    class Program
    {
        static void Main(string[] args)
        {
            int n = int.Parse(Console.ReadLine());

            for (int i = 1; i <= n; i++)
            {
                int sum = i.ToString().Sum(a => (a - 48));
                Console.WriteLine($"{i} -> {sum == 5 || sum == 7 || sum == 11}");
            }
        }
    }
}