// Simulate 1000 steps of interaction in the given star system; get the total energy in it as defined by the task.
public string PartOne(string[] lines)
{
var system = new System1D(lines);
system.StepTimes(1000);
return(system.TotalEnergy().ToString());
}
// Find out after how many steps the star system returns to the initial configuration.
public string PartTwo(string[] lines)
{
var system = new System1D(lines);
return(Enumerable.Range(0, 3).Select(system.StepAxisUntilSame).Aggregate(1L, LCM).ToString());
}