import java.util.Scanner;

class Main{
	public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
		String s=sc.next();
		sc.close();
		int t[]=new int[26],i;
		for(i=0;i<s.length();++i) ++t[s.charAt(i)-'A'];
		for(i=0;i<26;++i) if(t[i]>1) break;
		System.out.print(i>25?"YES":"NO");
	}
}