using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        string str = "aabbcdd";
        Dictionary<char, int> frequencyMap = new Dictionary<char, int>();

        foreach (char ch in str)
        {
            if (frequencyMap.ContainsKey(ch))
            {
                frequencyMap[ch]++;
            }
            else
            {
                frequencyMap[ch] = 1;
            }
        }

        foreach (char ch in str)
        {
            if (frequencyMap[ch] == 1)
            {
                Console.WriteLine("First Non-Repeating Character: " + ch);
                break;
            }
        }
    }
}