protected override object SolvePartTwo()
{
var wg = new ChitonCave(_bigRisk);
var aStar = new AStar <int>(wg);
var l = aStar.A_Star(new Point(0, 0), new Point((_rows * 5) - 1, (_cols * 5) - 1),
heuristic: (goal, next) => next.Manhatten(goal));
//DebugPrint(_bigRisk, l);
return(l.Skip(1).Sum(p => _bigRisk[p.Y, p.X]));
}