#Write a function that has one parameter - list of 
#integers and returns the average of the elements with 
#the EVEN index 

def ave_even_index(my_list):
	counter=0
	sum = 0
	for i in range (0, len(my_list), 2):
		counter=counter+1
		sum = sum + my_list[i]
	if(counter>0):
		ave = float(sum)/counter
	else:
		ave = -1

	return ave

def main():
	#What will be the output for each part
	#Part I

	my_list=[]
	print(my_list)
	ave=ave_even_index(my_list)
	print(ave)

	#Part II
	my_list=[3, 5, -5, 8 , 4, 7]
        print(my_list)
        ave=ave_even_index(my_list)
        print(ave)

main()