base64

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

namespace Base64__Контест_
{
    class Program
    {
        static void Main(string[] args)
        {
            StringBuilder base64 = new StringBuilder();
            List<string> alfavit = new List<string> { "A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z","a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z","0","1","2","3","4","5","6","7","8","9","+","/"};
            string binaryNumber = null;
            using(var sr = new StreamReader("base64.in"))
            {
                long n = long.Parse(sr.ReadLine());
                string[] str = sr.ReadLine().Split(' ');
                for(int i = 0; i < n; i++)
                {
                    for(int j = 0; j < str[i].Length; j++)
                    {
                        binaryNumber += System16In2(str[i][j].ToString());
                    }
                }

                long flag = 0;
                if(binaryNumber.Length % 6 == 2)
                {
                    flag = 2;
                }
                else if(binaryNumber.Length % 6 == 4)
                {
                    flag = 1;
                }
                if(flag == 0)
                {
                    long m = binaryNumber.Length / 6;
                    for (int i = 0; i < m; i++)
                    {
                        string temp = binaryNumber.Substring(i * 6, 6);
                        double index = System2In10(temp);
                        base64.Append(alfavit[(int)index]);
                    }
                }
                else if(flag == 2)
                {
                    long m = binaryNumber.Length / 6;
                    for (int i = 0; i < m; i++)
                    {
                        string temp = binaryNumber.Substring(i * 6, 6);
                        double index = System2In10(temp);
                        base64.Append(alfavit[(int)index]);
                    }
                    string lastString = binaryNumber.Substring(binaryNumber.Length - 2, 2);
                    lastString += "0000";
                    base64.Append(alfavit[(int)System2In10(lastString)]);
                    base64.Append("==");
                }
                else
                {
                    int m = binaryNumber.Length / 6;
                    for (int i = 0; i < m; i++)
                    {
                        string temp = binaryNumber.Substring(i * 6, 6);
                        double index = System2In10(temp);
                        base64.Append(alfavit[(int)index]);
                    }
                    string lastString = binaryNumber.Substring(binaryNumber.Length - 4, 4);
                    lastString += "00";
                    base64.Append(alfavit[(int)System2In10(lastString)]);
                    base64.Append("=");
                }
            }
            using (var sw = new StreamWriter("base64.out"))
            {
                sw.Write(base64);
            }
        }
        public static double System2In10(string str6)
        {
            double result = 0;
            for (int i = 0; i < 6; i++)
            {
                int temp = str6[i] % 48;
                result += temp * Math.Pow(2, 5 - i);
            }
            return result;
        }
        public static string System16In2(string str)
        {
            string result = "";
            switch (str)
            {
                case "0": result += "0000"; break;
                case "1": result += "0001"; break;
                case "2": result += "0010"; break;
                case "3": result += "0011"; break;
                case "4": result += "0100"; break;
                case "5": result += "0101"; break;
                case "6": result += "0110"; break;
                case "7": result += "0111"; break;
                case "8": result += "1000"; break;
                case "9": result += "1001"; break;
                case "A": result += "1010"; break;
                case "B": result += "1011"; break;
                case "C": result += "1100"; break;
                case "D": result += "1101"; break;
                case "E": result += "1110"; break;
                case "F": result += "1111"; break;
            }
            return result;
        }
    }
}