def couples(list):
	count = 0
	for i in range(0,len(list)-1,2):
		# print i
		if(abs(list[i]-list[i+1])!=1):
			count+=1
	if(count%2==0):
		return count//2
	else:
		return (count//2)+1
	return count

print couples([1,3,4,0,2,5])
print couples([3,2,0,1])
print couples([3,30,50,90,16,91,65,18,61,58])
print couples([3,1,5,4,6,2])
print couples([55,37,19,46,66,32,07,81,33,76,00,28,92,26,99,06,56,29,17,52,90,79,91,83,12,40,82,84,02,21,11,68,98,34,73,10,57,58,64,36])
print couples([1,0])
print couples([50,23,76,19,16,70,35,68,41,49,99,71,59,95,89,33,22,07,54,83,24,0,18,64,11,14,77,26,42,21,82,1,97,52,65,79,37,62,60,91,98,4,88,36,51,20,85,90,29,84,93,13,80,6,55,48,2,40,46,81,30,3,94,38,27,31,53,86,32,96,8,58,73,5])
