// Write a program that inputs number n > 0 and prints number of decimal digits in n.

// The program should use only integer numbers and only basic integer operations

// (addition, subtraction, multiplication, division). 

using System;

using System.Diagnostics;

public class Program

{

    public static int InputInt(string prompt)

    {

        Console.Write("Enter " + prompt + ": ");

        return Convert.ToInt32(Console.ReadLine());

    }

    public static void Main(string[] args)

    {

        int n = InputInt("n");

        Trace.Assert(n > 0);

        int d = 0;

        int ten_power_d = 1;

        // invariant: ten_power_d = 10**d and 10**d <= n

        while (ten_power_d * 10 <= n)

        {

            // ten_power_d = 10**d and 10**(d+1) <= n

            d++;

            // ten_power_d = 10**(d-1) and 10**d <= n

            ten_power_d = 10 * ten_power_d;

            // ten_power_d = 10**d and 10**d <= n 

        }

        // 10**d <= n and n < 10**(d+1) => n contains d+1 digits

        Console.WriteLine("Number {0} has {1} decimal digits", n, d+1);

        // Time = O(log n)

    }

}