inputer =input()
inputer_s =inputer.split(" ")
inputer_s.sort()
count_time = 0
result=0

while count_time <4:
	if count_time >0:
		if int(inputer_s[count_time])-tmp_d==1:
			result=result+1
	tmp_d=int(inputer_s[count_time])
	count_time=count_time+1

if result ==3:
	print("Yes")
else:
	print("No")