using System;

using System.Linq;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Enter a number");

        string input = Console.ReadLine();

        var inputArray = input.ToCharArray().Select(r => int.Parse(r.ToString())).ToArray();

        int oddOccurance = FindOddOccurances(inputArray);

        Console.WriteLine("Result:"+oddOccurance);

    }

    private static int FindOddOccurances(int[] array){

        var dictionary = new Dictionary<int,int>();

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

            var current = array[i];     

            Console.WriteLine(current);

            if(dictionary.ContainsKey(current)){

                dictionary.Remove(current);

            }

            else{

                dictionary.Add(current,i);

            }

        }

        if(dictionary.Count>1){

            Console.WriteLine("More than 1 unmatching element found");

            return 0;

        }

        return dictionary.First().Key;

    }

}