botanics

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Numerics;

namespace Q10127
{
    class Program
    {
        static private char[] par = { '1' }; static private BigInteger _n, sum; static private bool tof;
        static void Main(string[] args)
        {
            while (true)
            {
            label: Console.Write("N>>>");
                tof = BigInteger.TryParse(Console.ReadLine(), out _n);
                if (!tof||_n%2==0||_n%5==0) goto label;
                sum = 1;
                for (BigInteger i = 1; ; i+=2)
                {
                    if (i % 5==0) continue;
                    sum = _n * i;
                    if (sum.ToString().Split(par, StringSplitOptions.RemoveEmptyEntries).Length == 0)
                    { Console.WriteLine(sum.ToString().Length); break; }
                }
            }
        }
    }
}