Adv2015/D12.1/Program.cs

using System;
using System.IO;
using System.Text.RegularExpressions;

namespace D12._1
{
    class Program
    {
        static void Main(string[] args)
        {
            if (args.Length < 1) throw new ArgumentException();
            if (File.Exists(args[0]) == false) throw new FileNotFoundException();

            var input = File.ReadAllText(args[0]);

            int answer = 0;

            var regex = new Regex(@"(-?\d+)");
            var matches = regex.Matches(input);
            foreach (Match match in matches)
                answer += int.Parse(match.Value);

            Console.WriteLine($"The answer is : {answer}");
        }
    }
}