from numpy import*
alf = array(eval(input("qual a string? ")))

v = size(alf)
numb = array([])
for i in range(alf/2):
	min = alf[1]
	i = 2
	alf[i] = alf[i] - 2
	alf[-i] = min
	i = [i]
	print(v)
else:
	print(numb) #plsss i wanna die 