using System;

using static System.Console;

​

public class Program {

    public static void Main() {

        WriteLine("HelloWorld".ToCamelCase());

    }

}

​

namespace System {

    public static class StringExt {

        public static string ToCamelCase(this string text) {

            return char.ToLower(text[0]) + text.Substring(1);

        }

    }

}