using System;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        string s = "RLRRLLRLRL";

        Console.WriteLine($"Output: {BalancedString(s)}");

    }

    // Assuming there can be only 'L' and 'R' in the string

    static int BalancedString(string s) {

        CheckBalancedString(s);

        int count = 0;

        for(int i=0; i< s.Length - 1;i++){

            if (!s[i].Equals(s[i+1])) {

                count++;

                i++; // Next index is part of the set hence he hop it.

            }

        }

        return count;

    }

    static void CheckBalancedString(string s){

        Regex r = new Regex("^[LR]*$");

        if (!r.IsMatch(s)) throw new Exception("Sentence can only be made of 'L' and 'R' characters.");

        else Console.WriteLine($"{s} matches the expression.");

    }

}