x = [[1,2,3,4,5],[21,22,23,24,25],[31,32,33,34,35]]
y = [0,0,0]
z = [0,0,0,0,0]

def first():
	print(x[0])
	print(x[0][2])
	print(x[2][1:3])
	print(x[0][::2])

def second():
	for i in range(len(x)):
		y[i] = sum(x[i]) / len(x[i])
	print(y)

def third():
	for i in range(len(x[0])):
		for j in range(3):
			z[i] += x[j][i]
		z[i] /= 3
	print([int(i * (10 ** 2)) / (10.0 ** 2) for i in z])

first()
second()
third()