using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Text.RegularExpressions;

using System.Threading.Tasks;

​

namespace duplicateCount.cs

{

    public class Program

    {

        public static void Main(string[] args)

        {

            int count = 0;

            Console.WriteLine("Enter the String:");

            string str = Console.ReadLine();

            for(int i = 0; i < str.Length; i++)

            {

               for(int j = 0; j < str.Length; j++)

                {

                    string tempva = str[i].ToString();

                    string tempval = str[j].ToString();                  

                    if (tempva == tempval&&i!=j)

                    {                                              

                        str = str.Replace(tempval,"");

                        count++;

                        break;

                    }

                }               

            }

            Console.WriteLine(count);

            Console.ReadLine();

        }

    }

}

​