15.TextProcessingMoreExercise-Ascii Sumator

02. Ascii Sumator
Write a program that prints a sum of all characters between two given characters (their ascii code). On the first line you will get a character. On the second line you get another character. On the last line you get a random string. Find all the characters between the two given and print their ascii sum.
Example
Input                             Output
.
@
dsg12gr5653feee5                  363
?
E
@ABCEF                            262

using System;

public class Program
{
     public static void Main(string[] args)
     {
            var firstChar = char.Parse(Console.ReadLine());
            var secondChar = char.Parse(Console.ReadLine());
            var randomString = Console.ReadLine();

            var sumChars = 0;
            for (int i = 0; i <= randomString.Length - 1; i++)
            {
                if (randomString[i] > firstChar && randomString[i] < secondChar)
                {
                    sumChars += randomString[i];
                }
            }
            Console.WriteLine(sumChars);
     }
}