5.2(в)

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

namespace ConsoleApp1
{
    class Program
    {
        static int Func(int n)
        {
            int k = 0;
            if (n % 2 != 0)
                k++;
            if (n / 10 != 0)
                k += Func(n / 10);
            return k;
        }


        static void Main(string[] args)
        {
            Console.Write("a=");
            int a = int.Parse(Console.ReadLine());
            Console.Write("b=");
            int b = int.Parse(Console.ReadLine());
            int mx = -1;//max
            for (int n = a; n <= b; ++n)
            {
                int m = Func(n);
                if (m > mx)
                    mx = m;
                //Console.WriteLine("{0}={1}", n, m);

            }
            for (int i = a; i <= b; ++i)
            {
                int m = Func(i);
                if (m == mx)
                    Console.WriteLine("{0}", i);
            }
            Console.ReadKey();
        }
    }
}