Main Question or Discussion Point
A snake with a little more than 4 meters takes a walk for the forest in the following way. After to walk 1 meter in definitive direction it decides aleatoriamente if she capsizes for the left or if she capsizes for the right or if she continues in the same direction, independently of the previous decisions. However, if at some moment it finds its proper tail, it does not recognize it, bites and dies poisoned. She determines the probability of that the snake walks at least 10 meters before dying.