using System;

using System.Text;  

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        StringBuilder sb = new StringBuilder();

        sb.Append("5,5");

        sb.Append(",");

        sb.Append("7,9");

        sb.Append(",");

        sb.Append("4,7,6,1");

        sb.Append(",");

        sb.Append("1"); 

        string[] arr = sb.ToString().Split(',');

        int[] test = Array.ConvertAll(arr, s => int.Parse(s));

        var count = test

            .GroupBy(e => e)

            .Where(e => e.Count() == 1)

            .Select(e => e.First()).ToList();

​

        foreach(var item in count)

            Console.WriteLine(item);

    }

}