import java.util.HashSet;
import java.util.Scanner;
import java.util.Set;

public class Main {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		String S = scan.next();
		scan.close();
		Set<Integer> set = new HashSet<Integer>();
		for(int i = 0; i < S.length(); i++) {
			char c = S.charAt(i);
			set.add((int)c);
		}
		if(set.size() == S.length()) {
			System.out.println("YES");
		}else {
			System.out.println("NO");
		}
	}
}