using System;
using System.Linq;

public class Kata
{
  public static int problem(int A, int B)
  {

         int z = A - B;
        Console.WriteLine("The z number that" + z +"    " +  z.ToString().Count());
            var q = z.ToString()
                .ToCharArray()
                .Select(x => char.GetNumericValue(x))
                .ToList();

            for (int i = 0; i < q.Count; i++)
            {
                if (q[i] >= 1)
                {

                    if (q[i] == 1 && i == 0 || q[i] == 1 && i == q.Count - 1)
                    {
                        continue;
                    }
                    else
                    {
                        q[i] = q[i] - 1;
                        var Q = q.Aggregate("", (c, n) => c + n);
                        Console.WriteLine("the return value. "+ Q +"    "+ Q.ToString().Count() );
                        return Convert.ToInt32(Q);
                    }

                }
            }

            return 0;
}
}