using System;

class D
{
	static double[] ReadDec() => Array.ConvertAll(Console.ReadLine().Split(), double.Parse);
	static (double, double) Read2D() { var a = ReadDec(); return (a[0], a[1]); }
	static void Main() => Console.WriteLine(Solve());
	static object Solve()
	{
		var (h, r) = Read2D();
		return -8.245 + 6.807 * h + 7.073 * 2 * Math.PI * r;
	}
}