using System;

public class Program

{

    public static void Main()

    {

        var valorEmReais = 15;

        Console.WriteLine(FormatCurrency(valorEmReais * 100));

        Console.WriteLine(FormatCurrency(150L));

        Console.WriteLine(FormatCurrency(15L));

    }

    public static string FormatCurrency(long value)

    {

        var str = value.ToString();

        var len = str.Length;

        return len <= 2 ? $"0.{str.PadLeft(2, '0')}" : $"{str.Substring(0, len - 2)}.{str.Substring(len - 2)}";

    }

}