using System;

​

public class Program

{

    public static void Main()

    {

        string a;

        char b = 'в';

        Console.WriteLine("Type your words:");

        a = Console.ReadLine();

        int index = a.IndexOf(b);

        if(index == 0){

            Console.WriteLine("Not found B");

        }

        else{

        Console.WriteLine("Found B Under the number :");

        Console.WriteLine(index+1);

        }

    }

}

​