public class MonstersAndBunnies
{
	public double survivalProbability(int M, int B)
	{
		return ++M%2./M;
	}
}

double Prob(int M)
{
  if (!M)
    return 1;
 
  if (M % 2)
    return 0;
 
  return (M - 1.0L) / (M + 1.0L) * IT (M - 2);
}
 
double
MonstersAndBunnies::survivalProbability(int M, int B)
{
  return Prob(M);
}

Order the monsters together with yourself in the order that you're called up to fight. You live iff the number of monsters is even and you're last in the order

Order the monsters together with yourself in the order that you're called up to fight. You live iff the number of monsters is even and you're last in the order.

Is this a direct conclusion of M!/(M+1)! ?