using System;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        var formula = "Na25Cl3";

        var atomos = Regex.Split(Regex.Replace(formula,"\\d",""), @"(?<!^)(?=[A-Z])");

        //var atomos = Regex.Split(formula, @"(?<!^)(?=[A-Z0-9])");

        var numeros = Regex.Split(formula, @"(?<!^)(?=[A-Z0-9])");

        print(atomos);

        print(numeros);

    }

    public static void print(String[] array){

        Console.Write("[");

        for (int i = 0; i < array.Length; i++){

            Console.Write(array[i]);

            if(i < array.Length -1) Console.Write(", ");

        }

        Console.Write("]\n");

    }

}