Red Hunter Piranhas

Problem description. Red Hunter Piranhas are the most dengerous fishes in the ocean, they attack on their prey in a isosceles triangular formation. Such that, i'th level of Piranhas in the triangle contains 2^(i-1) fishes and let's give a id number to each fish, such that, number of first fish in i'th layer is 2^(i) and second fish have id 2^(i) + 1 and so on. Considering that each fish will only