using System;

using System.Collections.Generic;

using Newtonsoft.Json;

using Newtonsoft.Json.Serialization;

​

public class Person

{

    public string Name { get; set; }

    public string Surname { get; set; }

    public int Age { get; set; }

}

​

​

public class Program

{

    public static void Main()

    {

        var source = "020406081012141618202224262830323436";

        var result = InsertEach(source, Environment.NewLine, 10);

        Console.WriteLine(result);

    }

    public static string InsertEach(string source, string insertValue, int interval)

    {

        var lengthOfNewLine = insertValue.Length;

        for (var i = interval; i < source.Length; i += interval + lengthOfNewLine)

        {

            source = source.Insert(i, insertValue);

        }

        return source;

    }

}

​