HashSet visited = new HashSet(); int sum = 0; foreach (var v in Enumerable.Repeat(File.ReadAllLines(Path.Combine(Path.GetDirectoryName(Util.CurrentQueryPath), @"01_input.txt")).Select(int.Parse), int.MaxValue).SelectMany(p=>p)) { sum += v; if (!visited.Add(sum)) { sum.Dump(); return; } }