gets
point_cnt=gets.chomp
point=point_cnt.split.map(&:to_i)
even_dis=0
odd_dis=0
(point.size-1).times do|i|
if(point[i]+point[i+1])%2==1
	odd_dis+=1
else
	even_dis+=1
end
end
if odd_dis>even_dis
answer=(odd_dis-(even_dis+1))
else
answer=(even_dis-(odd_dis+1))
end
print answer