removeRepetingCharacters

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Text.RegularExpressions;

namespace ConsoleApplication3
{
    class Program
    {
        static void Main(string[] args)
        {
            string input = Console.ReadLine();
            string pattern = @"(.)(?!\1)";
            string result = string.Empty;
            Regex regex = new Regex(pattern);
            foreach (var item in regex.Matches(input))
            {
                result += item;
            }
            Console.WriteLine(result);
        }
    }
}