func main()
	var ss: [][]char :: cui@input().split(" ")
	var a: []int :: #[4]int
	for i(0, 3)
		do a[i] :: ss[i].toInt(&)
	end for
	do a.sort()
	var ans: bool :: true
	for i(0, 2)
		if(a[i] <> a[i + 1] - 1)
			do ans :: false
		end if
	end for
	do cui@print(ans ?("Yes\n", "No\n"))
end func