reiwa.cs

using System;
using System.IO;
using System.Net.Sockets;
using System.Threading.Tasks;
using org.mariuszgromada.math.mxparser;

namespace reiwaCTF
{
    class Program
    {
        static async Task Main(string[] args)
        {
            var client = new TcpClient();
            client.Connect("zerois-o-reiwa.seccon.jp", 23615);

            var stream = client.GetStream();

            var sr = new StreamReader(stream);
            var sw = new StreamWriter(stream);
            while (true)
            {
                var input = sr.ReadLine(); Console.WriteLine(input);
                input = sr.ReadLine(); Console.WriteLine(input);
                var q = input.Replace("0=", "");
                sr.Read(); sr.Read();
                var ex = new Expression($"solve({q.Replace("?", "x")}, x, 0, 10000000)");
                var result = ex.calculate();

                Console.WriteLine(result);
                sw.WriteLine(result);
                sw.Flush();
            }
        }
    }
}