func main()
	var S: []char :: cui@input()
	var a: []int :: #[26]int
	var ans: bool :: true
	for i(0, ^S - 1)
		do a[S[i] $ int - 'A' $ int] :+ 1
		if(a[S[i] $ int - 'A' $ int] > 1)
			do ans :: false
		end if
	end for
	do cui@print(ans ?("YES\n", "NO\n"))
end func