static void Main(string[] args) { BigInteger[] ints = new BigInteger[100]; string[] vals = numbers.Split('\n'); for (int i = 0; i < ints.Length; i++) { ints[i] = BigInteger.Parse(vals[i]); } Console.WriteLine(ints.Aggregate((result,next) => result += next).ToString().Substring(0,10)); Console.ReadKey(); }