3rdIs7

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

//Write an expression that checks for given integer if its third digit from right-to-left is 7

class ThirdDigitIs7
{
    static void Main()
    {
        uint intToCheck;
        int needle = 7;
        Console.WriteLine("Provide an positive integer to check:");
        while(!uint.TryParse(Console.ReadLine(),out intToCheck))
        {
            Console.WriteLine("Please, enter valid integer.");
        }
        int thirdIntInDigit = Convert.ToInt32(Math.Floor(intToCheck / Math.Pow(10, 2) % 10));

        Console.WriteLine("3rd digit in {0} is 7? {1}", intToCheck, (thirdIntInDigit == needle)?"True":"False");

        Console.WriteLine("\nPress any key to exti.");
        Console.ReadKey();
    }
}